Can I have some tris in my model made up of quads? Firstly, I dont have that much experience with blender or 3d modelling. Im making a character for a unity project and would like to know if my model should only be made up of quads or is it ok to have some tris in it as well. 

I only ask because I've been ending up with a few tris when I'm near to completing the model.

Also what are some ways of converting tris to quads manually.  I have used the "tris to quads" option without success.

Thanks for the help.
Unity only struggles with N-gons, which are polygons made of 5 or more vertices, so you shouldn't have problems if you have some triangles in your model.