This should not be difficult. If you really think you deserve a raise you dont need to think on how to ask for it. If you are convinced that you have done work that makes you eligible for a decent hike, then be straightforward. Ask for some time for discussion with your boss and just list down the good things you have been doing and clearly tell him/her that you deserve a hike. He/She might want to avoid it by saying no budgets, company policy etc etc but trust me managers can always pull hikes for their subordinates if they want. So be polite but firm and list down the things in detail till you convince of your contribution. Now the tricky situation can be hen you know that you havent done great enough to list don things. Frankly and honestly, in such a situation i personally will not fight for a raise. If I am myself not convinced of my work, I will not even try convincing anyone else.