I agree with the above stuff, just had a few things to add.
You should think hard about what procedure you will use to set the spinnaker and then what procedure you will use to douse it. What will you do first, how will you rig it before launching it, who will do what, etc, etc. There's a lot of stuff to do and it's nice to know what the steps are and who on your crew will play what role
Second, the way the spinnaker is packed can make a big difference in how easy the set goes. Make sure it's packed correctly and that you kind of have idea of how it's going to come out of the bag.
Third, how will you deal with the spinnaker if it has a twist in it.
Last just to second what Faster said, try and find a relatively stable day weather wise.
Last, last...do you belong to a club or know other sailors? Maybe you could invite someone to go out with you the first time you fly the spinnaker to learn from them