Flower advice needed

[AF-NCO]

I've been inspired by both the recent purchase of my 20D and seeing all these great flower photos on here. I'm going to pay a visit to Phoenix's botanical gardens tomorrow and see if I can get some good shots. Since I new to this kind of photography, does anyone have any suggestions when it comes to taking pics of flowers? Shutter speeds, DOF, etc.? Unfortunatly, my recent purchase has also left me broke, so I don't have any flashes, and only 2 lenses to work with (Cannon's 17-85 IS, and the 75-300 IS).

Thanks in advance for the advice and pray for good weather for me!

[PhotosGuy]

I like a very shallow DOF. JZaun usually goes for a bit more, & his flower shots are great. (Before he eats them in a salad!) Why not search his posts & see what appeals to you? ;-)
Are you going alone? A 11X14 white card can provide some nice fill light if you have someone to hold it.