Depending on the enemy team you can build Mercury Treads instead of Ninja Tabi,Thornmail instead of Sunfire Cape,Force of Nature instead of Thornmail

When you go solo top Lee Sin try to harass your enemy at early levels(i start at level 2) and try to farm as much as possible.
When you are playing jungle gank at level 2, right after red camp(where you start jungleing) and gank as much as you can.

When in teamfights try to use your ultimate to knock enemy squishy champions into youre team to ensure you win the teamfight.