Learn your champion's defensive tools and gun them.
In mid lane, most Assassins for example can easily dodge abilities, for example. Yasuo is obvious against projectile users, Talon and Katarina teleport behind their targets to negate skill shots, and Zed goes full on untouchable for a moment. This opens up opportunities for counter engages, and if you can play it right, turning around a losing lane.
Top lane tends to be a bit more of a mixed bag in terms of defensive tools, but I shit you not timing your lockdown abilities with your minion aggro wins trades. Let's say it's Maokai vs Renekton, and Renekton gets an early lead. If Renekton dashes in and hits Maokai with an auto attack, a quick Twisted Advance can pin Renekton down while all the minions around them start attackng Renekton. Any mistake by Renekton and/or if Maokai has good timing, and you can almost literally have minions win the trade for you.
As for Nidalee specific advice, I recommend learning to time your aggro. Take time to notice whenever the opponent blows an important ability, for example if Ahri uses her Orb of Deception to poke (and you hopefully dodge it) or to farm. The moment it's on cool down, try to land a Spear or a Trap and engage on Ahri. She can't fight back at full strength; her Orb is on cool down after all. I can certainly say though that Top Lane is a bit harder, since Nidalee doesn't really have a way to punish people for drawing minion aggro.
