One of the hardest things about sewing is working out how to fit yourself- but it's also the most rewarding -and often the reason we started in the first place! As a beginner though it is very hard to know where to start. There is a wealth of tutorials out there for every fitting dilemma, but without knowing what you are googling its harder to find them.
I have therefore made a diagram with many of the common fitting changes on it. Obviously I haven't included everything - but I hope I've got most of them (let me know if you think any obvious ones are missing!). I have also not included any links (except to the insanely thorough pants fitting guide by Colette patterns which is amazingly detailed and I know nothing about pant fitting myself!) as everyone finds different resources helpful and I certainly haven't seen the whole internet!
I've done it by body area, and generally stuck to things which wouldn't automatically require you to just make a different size -though I have pointed this out as an option in some places. For each problem I have just listed possible solutions -obviously you need to look at your body and google stuff and see which one is likely to help you.
I hope this is helpful!
(EDIT -for some reason the image isn't coming up on mobiles-probably too big, so click through to the full page if you want to see it or here.)