1st trip to the Zoo with the 55-250IS…What can I do?

Straight from the camera...

1.

Glass is particularly hard... You need to put the lens flush to the glass and/or make sure there's no light entering between the lens and the glass.... even then, reflections may crop in.

Other than that, if this is your first time out, I think it looks great! I'd probably go with less DOF, but based on the EXIF information, looks like you might already be shooting wide open. I don't want to post my own zoo pictures in your thread, but if you're interested, I'll throw them up somewhere too!

6. and 8. were the only two through glass...

I can see the glass in some of my others so I'll have to remember to stay tight against the glass...

Yeah... #1, try and get close to the "cage" and maybe even zoom less to get a shallower DOF... but there's not much you're going to be able to do beyond that. Only success I've had in that situation is to shoot my 85mm f/1.8 wide open, and then the front part of the cage disappears.

I've used my hand on the hood of my 70-200mm f/2.8L IS to try and shield against glass reflections with moderate success too....

I want some L in my life...

it helps, but given the right circumstances, you can do a lot with what you've got. This shot is a substantial shot of a full-body shot with my 40D and 70-200mm f/2.8L IS:

http://www.drjpics.com​/jpg/zoo/IMG_7295S.JPG

Like I said, it helps, but I think you can do a lot with what you've got, and you have more reach too!