What are early signs of diabetes? And what kind of testing is done to check for it?

I bruise easily and was told it could be a sign of diabetes. I am only 27. Also what do doctors do to test for diabetes? Also I get light headed sometimes, hotflashes, can go from happy to sad at times,I do urinate frequently but always have,sometimes I feel weak like I dont have energy [...] http://bit.ly/nZ73OO