PSA: If you have a lead and do nothing with it you are just as useless as someone who's behind
Let's set the stage: You have won your lane or made a few jungle ganks netting kills or assists. You are now ahead in items and probably levels. You can probably 1v1 anybody uninterrupted. In this situation I see people all the time who just freeze their wave in the middle of their lane and last hit, not even harassing the enemy. While you may be zoning them off some because they fear you, you are actually letting him catch up, or other lanes make up for the difference. You are strong. Here are a few things you can do if your ultimate is up: Go deep ward, go to another lane and force towers, group and force dragon, kill or even shove the enemy out of lane denying him. Freezing the wave in the center of your lane is not using your lead. Jungle is mostly the same. If you are tanky you can even force dives which result in a tower and dragon or rift herald. You have the option to safely counter jungle. Make sure you can see all the laners and drop a ward where they might come from. If you find the enemy, kill him or force him out. He is weaker than you. Also take camps if you can. This will set him behind more. These things will help you keep your lead, and win more games