If I was you, I'd list your favorite top champions, since it may help us give tips (for instance, my main tops are Poppy and Karma, so most tips applies differently).
Otherwise, like Large said, Darius is by far the easiest for most champs (anyone with a movement spell has a really easy time against him, and so does other bullies like Darius). The main points I suggest to you for this matchup :
- If you can afford to do so, pressure the lane at level 1. If you manage to hit level 2 2-3 minions before him, you can really set him back hard.
- Easier said than done, but dodge those Q spins.
- Ask for jungle pressure to snowball ahead of hm pre-6.
- If any of the previous 3 fails, fall back to point #4 : Farm under turret. Unless he has already snowballed, you should be able to get ~5 minions per waves, meaning he won't pull much ahead.
- End your laning as fast as posible if you're behind. Whenever I'm against a Darius that we're past 10-15 minutes and I'm losing, I will roam/teleport mid and shove 1-2 turrets + dragon. Sure, he'll get a bit of free farm and probably a tower, but if you get more than that you won your trade, and if you don't you can still outscale him in teamfights (in most cases).
For Jax/Renekton, they're simply very strong, so basically, try to trade damages only when you have 5+ more minions than he has, the damage really adds up. Also they're 2 extreme bullies in lane and a tad weaker in teamfights, so against all 3, I would suggest you to actually peel for the carris if their top is trying to dive. He can't 1v2 you ever unless either of you is terribad, and as long as the last 3 aren't totally stupid to go into a 3v4, the ywill stall the fight and their top will get chunked heavily.