Runner's Training Tips: training on flat or hilly courses

Hi, I am fairly new to running, and have signed up for a few 5k and 10k races this year. The races are all described as flat and fast, and I'm wondering about my training tactics. Should I just train on flat and fast tracks or include some hills as well? So far I've been training on flat courses, but I'm getting bored with it, and want to add hills for variety and challenge. Does any of this even matter as far as my training? I would like to improve my time, and figured that hills might improve my stamina and endurance. Please give me your take on this! Thanks.

Even though your races are on flat courses, it always helps to work in hills.......just don't go crazy with them.  Since you say you are interested in improving your speed.....t sounds to me like you are ready to work in some speed sessions (tempo runs).  Doing a few tempo runs will also put some variety into your routine.  This way can do a few regular pace runs on the hills and....and maybe a few on flat course....and a tempo/week on flat as well.

Someone once said... "Hills are like speedwork in disguise".

I don't know who it was, but those are words of wisdom.

Also, I would say; mix your routes i.e. don't do the same everytime, run at different paces, explore your neighbourhood, run in different conditions, at different times of day etc.

Also, mix in other sports if you can, or it will get boring ;o)