Let's just cut to the chase. We will first get to the basics in order to build a solid foundation and then move on to some intermediate and advanced concepts. I would like to apologize in advance if I've just stated the obvious and/or sounded condescending in the process. I genuinely want to help you (and myself) in becoming a better player :D

- eDPI: Here is a list of eDPI of pro valorant players (they have an average eDPI of around 250-270). I would recommend you to have an eDPI between 150 (really low)-400 (medium; "Shroud sens"). You may also watch this video to get to the right sens.

- Aim Mechanics: This video by Ron Rambo Kim is great for understanding the different types of aiming techniques and mouse grips (wrist aiming, arm aiming). Remember, consistency in your posture is key. Make an effort to always get into the exact same posture whenever you get into a gaming session. If you are not using a table and chair (I am pretty sure that you are), only the Valorant gods can help you.

- Perspective: Understand the importance of perspective. It is always better to stand as far away as possible from the wall you are going to peek from. This is completely because of perspective. This video explains this thing pretty well.

- Counter-strafing: If you haven't mastered counter-strafing yet, do it (but be careful NOT to wide peek). This way, even if you face more than 1 enemy, you can take your gunfights one at a time. You may watch this vid to understand how this works. Also, note that run and gun is sometimes effective. Refer to this video from a Tenz stream. These two things might sound counter-intuitive at first but understand that the distance and the gun you are using is important (It's easier to do it with a phantom in close range for example). As a general rule of thumb, if you aren't sure, don't run and gun unless you are really close.

- Handling 1v1s: In an ideal world, the player with the better aim shall win any 1v1. However, factors like crosshair placement, ability usage, positioning and jiggle-peeking decide who actually wins the 1v1. If you are playing with an agent with flashes or a damaging/distracting ability like raze's boombot/nade, you shouldn't be dying without using them. Don't engage in 1v1s where you are at a clear disadvantage (Smoke that sniping Jett on Haven C long or don't peek Ascent mid with a shorty for example). Only take such duels, if you MUST and try to handle these situations smartly. When you are in a 1v1 vs an Operator, jump/shoulder peek to bait out a shot first (it's a bit tough but practice in deathmatch or range and you'd be fine). You can also jump and peek with a Judge/ maybe even the Bucky. Lastly, some people like to jump peek with a classic, as the firing error is minimal with it.

- To crouch or not to crouch? : In lower elo, not many players are going to have perfect crosshair placement. By crouching, you would only increase the chances of the opponent landing a headshot or being quickly traded out by one of their teammates (as your movement speed is hugely reduced). Jiggle-peek is mostly a better option. Once you get to higher elo, crouching may be useful in 1v1s (but it STILL completely depends on the situation). It is better to know how to handle an opponent crouching (either crouch yourself or burst fire and re-aim to his head).

- Know your weapons: Make sure to be aware of the advantages (and disadvantages) of the weapon you are using. Example: You only want to take very short range engagements with a Judge/ Shorty/ Stinger. Some weapons are meant for spraying (Ares, Odin) while others are better if you tap/burst with them (Guardian, Vandal). For other weapons, you have to assess the distance between you and your enemy (you can't spray with a Frenzy if the enemy is more than 10 m away from you). This video may be helpful.

-Economy : Understand "Save" rounds. For example, if you lose the gun round, it is pretty common to save your credits in the second round so that you can buy Phantoms in the third round. With the recent patches, it is sometimes better to die than save a cheap gun. Example, you should insist on dying from the spike when you have a gun with less than 1600 value and no shield. It doesn't count as a death on the scoreboard (now) and also adds additional money in your economy. If you are in 1v5 defense situation on defense, it is mostly a good idea to save your phantom/vandal/operator. If you have a cheaper gun, it is worth trying to get at least a few picks (to damage opponent economy and get some extra credits + kills).

-Lineups : Sova, Brimstone, Viper, Killjoy and even Raze have some really good lineups for both post-plant, entry and retakes. It would be super easy to win a round if you have got the plant down and there are less than 15 seconds left before the spike detonates.

-Communication & Mini-Map : Make a habit to use comms (Don't forget to mute the toxic losers ASAP). They are never worth your time. I understand that most people in Iron 1 won't understand your callouts or would themselves give any callouts but it is a good habit to develop. Also, make a habit of glancing at the minimap to know what your teammates are up against or trying to do (Example 1:No need to peek on defense if your teammate is very close to executing a flank; Example 2: If your teammate just died to 4 people in Haven C long, don't make the mistake of peeking all of them on your own).

- Playing Attack: If you are attacking a site, it's never a good idea to hurdle up together with all your teammates and push recklessly inside. Even if you are rushing a site, you should leave enough space between you and the teammate in front of you so that you can react to his callout/ what he is seeing on the map/ how he died. This will enable you to get easy kills, trades and site control. Be wary of short range weapons like the Judge- either force them to take a long range duel with you or force them out of their position using abilities. Either ask one of your teammates to watch flanks or do that yourself. While pushing any part of the map (even while rotating), always clear each and every corner. You would learn how to do this quickly with time. You can watch thisto get some additional tips.

- Playing Defense: While defending, if you face an opponent rush, it's better to back off and take a 5v5 retake. This is a tough thing to do in practice but is going to pay dividends as the opponent would have used up all their abilities while your team would still have all abilities left. Sometimes, when the opponent team is "playing for picks", you may attempt a flank (but do not keep flanking as this is something that offers diminishing returns). While flanking, always clear each and every corner.

- Watch Streamers : This post by u/Satwik_Pandey has a pretty comprehensive list of streamers who main a particular agent. Watch them to have a better idea of how to play each agent on a given map.

- Play with a Stack : It is fine if you can't always find a 5-stack all the time but even a duo-Q is way better than Solo-Q. However, you must make use of clear communication with your teammates because if you don't, what's the difference between a 5-stack and a set of 5 Solo-Q players?

- Hardware and Setup : It is pretty necessary to have an good mouse (examples: Logitech G102, Razer Deathadder, Corsair Harpoon) and a reasonably large mousepad. Don't fall for BS marketing for mice (like 2000 DPI and stuff). Also, it is not impossible to get out of iron without these but it is definitely a lot more difficult. You may already know that a 144 hz monitor is way better than a 60 Hz monitor and would offer a much smoother experience. Also, if you aren't getting 120+fps in your game, you may consider upgrading your PC. Note: I am not telling you to spend a tonne of money on these things. Only buy what is feasible and no need to fret over it if you are not earning yourself.

- Additional Tips for Comp : Warm-up your aim in Deathmatch before going into a Ranked game. Don't tilt and mute anyone who is being toxic at the first offense. The positives from their callouts (which they seldom make) far outweigh the negativity that they spread. Don't instalock an agent. A game is still winnable with 4 duelists but it's better if you have one smoke agent (Omen pick rate in Pro games is 90%). Try to pick duelists yourself (but don't instalock) as long as you are in Iron/Bronze as it is tough to get frags as a support player and if your duelists teammates aren't performing, you would feel helpless. Regardless of the score, be confident in your abilities. I have seen cracked Sage players carrying in Immortal lobbies. It is definitely possible albeit difficult. Maybe dodge games that you feel are gonna end up bad (toxic Reyna spamming pick sage or Insta-locking jett telling you to pick Omen). Whether it is attack or defense, never be predictable or go into auto-pilot mode. React to what the opponent is doing (you shouldn't be losing 5 attack rounds to flanks or 4 defense rounds to rush).

-Most importantly, have fun!

Note: I would be adding more relevant info from the comments in Edits in order to make this post as comprehensive as possible.

Edit 1: Formatting and grammar

Edit 2 (on the recommendation of u/gavina2003 ):

- The Right Mentality:

You should obviously try to win games, but you must accept that you will lose. Having a strong mental is literally required if you want to climb or improve at all.

Although it may sound counterintuitive, don't fret about your rank too much. Just like sportspersons focus on the very next game at hand, whilst taking things step by step, we should also prevent ourselves from getting overwhelmed by the huge climb. Focus on the current game, heck, even the current round. This would help you in keeping sane while ranking up.

Edit 3:

- Natural Markers for Crosshair Placement: Basically, this video by eggwick (and more on his channel). It is pretty self-explanatory. Watch if you are interested for some easy hacks.

Edit 4 (on the recommendation of u/IronCrown): Changed the word "lightweight" to "good" in Hardware part of the post. Also requested newer players to not fall for BS marketing.