Hug the turret, get whatever experience you can. Champions who can farm from distance can deal with 1v2. you'll get exp. advantage, if you do no die. Talk to your jungler to let you top jungle to farm it (assuming they have duo top they do not have jungler, so your jungler can farm enemy jungle). Most important thing: do not die. Even if you are behind at CS if you do not give them kills they will fall off. Coordinate with your jungler, maybe help him gank mid.. Sometimes it is better to abandon tier one turret, let them take it and freeze in front of 2nd turret. Still it is up to the champion, if he can freeze ealy or farm under turret. Anyways - if they are under your second turret easy ganks for your team. Still it is better if your midlaner and jungler come toghether, because depending on champs there is a chance to lose the 2v2.
If they want to fight - build tanky and try to bait them to towerdive you, then try to CC them under the turret. Never be the one, who initiates. Chances are to still lose the fight, but at least you have chance to take a return kill.
Whatever you do 1v2 the rest of the map is 3v4. Your team must take advantage of that. It sucks that you just derp there and wait to be carried, but if you and they are equally skilled - that's the only thing. Also baiting and outplaying under your turret, but it is still situational, so do not take risks.
