Newbie needing help laning 1 v 2

Hi everyone. I was wondering where I can find a reliable guide to surviving a 1 v 2 situation. In many of the games I play, I end up having either no support or no proper support. As such, I end up laning 1 v 2 about half the time.

In particular, I'd like to know what appropriate times I can trade or harass or tips about farming under the tower when I'm playing against poke combos. Even in a dire situation like that, it would be good to salvage something out of it.

Tips and hints are welcome! Thanks in advance for any help. :)