Make sure to farm as much as possible and do damage to your opponent with your tornadoes or your lane harass combo (E in>Q>E out) when they get low don't be afraid to go really hard. Another good thing to keep in mind is to give your jungler only a mediocre leash allowing you to get more XP then your opponent. Your main goal is to kill them before they get their power spike OR before the hit lvl 6/first back.

By now you should have killed your opponent 2-3 times and you should have there tower and a statikk shiv now you can have some fun and start roaming to help other lanes or keep riding your opponent's **** so they have minimum impact in the over all game.

If they haven't surrendered yet then clearly you or your team mates are doing something wrong, try your best to have already gotten baron and have a full build before 18. start looking towards split pushing and possible multi kills so you can push down one of the lanes to win.

If you have been playing for more then an hour then you are wasting time and should surrender because you have better things to do in life like raping the teemo player that lives across the street or hallway.