I just started cruising solo a few months ago so I am still pretty new at it. But here goes, be sure to see the maitre'd when you first board. He is undoubtedly putting one or more tables of solo travelers together and will be happy to move you. Also, be sure to introduce yourself to your cruise director and let him/her know that you are traveling on your own and would like to meet others. On some ships there are singles get togethers the first day or two.
Kristi-Rae, thanks for posting the advice regarding cruising solo and letting the maitre d' and cruise director know about it. But don't stop there. The cruise director is extremely busy and will, of course, do whatever he/she can to accommodate, but it also helps to go around and meet the other members of the cruise staff.