What to do with slow Android phones?

Most of android phones become slow after few months of use, My question is how we can make them fast again? even i have mobile with 2gb mobile 10gb storage and I just use few specific apps like twitter, fb, outlook and that’s all but I can’t even quickly make a call… i rest many time and change other models but still same issue, phone become slow after few months… plz guide me whats the main issue.