Open Question: What can help to relieve constipation so i can have a poo?

I've got constipation and at the moment because of it i'm feeling a niggling pain in my lower abdomen, but i don't know whether it is from constipation or because i trained my abs hard yesterday, so it could be either one, but i have constipation and it's annoying me because i have had no sign of bowel movement yet. What should i eat or do to help improve it?? I really want a poo, just so i can have that relieved feeling.