Another way also to learn how to keep the right tempo is to try to sing the song to yourself before you start playing. I had that trouble alot, and I actually had to get my dad to count for me while I practiced. However, I have found that singing the song to yourself really works.
Also, if you have a metranome, or a keyboard with a beat, play a song that is usually fast (like Victory is mine/This is the day) at a slower tempo. This REALLY teaches you how to play with the tempo, because you have to pay very close attention to not playing the song as you are used to playing it.
I hope this helps, because I have been there before, and sometimes find myself slipping thereeven now.
(sometimes I even type so fast that more words get all mumanmnk up ajdf u cnt evn rede wat I tipe!) HAHAHAHAHAHA...... JK