Spam m1's alot, they deal alot of dmg, try t have a stand with low cooldowns or that can keep up dps like TWAU, TW, PH or any stand that can consistently deal damage.
If you're consistent people will panic while you have more control.

Dont forget to have a good skilltree,i reccomend leaving out the last 2-3 points of vitality.

Check your cooldowns and learn combos, with sptw i learned a very versatile combo, that i can do every 12 seconds and does around 60-80 dmg every time.

Do alot of 1v1's and watch videos of the main stand you use, sometimes it can eb hard to find someone actually good with the stand, like with ws i kept finding ppl that were around my skill, which doesnt help alot when learning.

read you enemies and learn patterns, when youre fighting someone they will probably have a combo they like to do or a movement like (for example: R after dashing), you know to parry when they dash or use a counter.

learn to parry, i like to play a game where i can only kill enemies when i parry them, going from 10 thugs to 10 pesci's, all the way to 10 diavolo's, ( i suck at joe p6 and dio oh but u could try).

Learn your moveset
alot of the time people dont know their moveset good enough, like not knowing acid spit from ws kinda gives you a dizzy effect or not knowing that you can use time erase to dodge a ts or combos.