Note:this might not work for the one that has rating beyond specialist.
Most Poeple will say that you should solve problems that are harder than your current skill.I feel like this advice is really bad.In fact,it is one of the worst advice i have ever heard(for newbies).Why? because i have tried and i just ended in a loop of desperation like other people that post blogs about how to get rating X.
Whenever you do not understand a problem,you read the editorials.This is good,you know what the solution is.However,does your intuition improve? Most editorials will just present you with the actual solution,rather than actually triggering your brain to think into the correct way.This is very crucial and i feel like without this,people will just see editorials again and again and they will just want their time and eventually quit or cheat every contest.
So,my advice is only 1.Find a mentor.A mentor that can help you to think not like editorials.I found a trainer and you won't believe how much i improved.I am able to solve 3 problems for the first time.Before getting a mentor,i just see editorial and understand.My thinking skill does not develop.
For those who want to get a better rating,stop trying.You will not be better if you continue to just solving problems that will overwhelm you.You may be able to solve a problem in a specific rating,but you are not guaranteed to solve other problems with similar rating even though you have tried other problems before.You need a proper guidance that is professional enough to stimulate your brain by helping you solve problems live.