Hi glad you are interested in what is one of my favorite hobbies....in general, take your time to stretch and warm up, for many later in the day is better when your body has been active all day rather than first thing in the morning....less food in your stomach is good too....be sure and stretch both ways front bending and back bending to keep the spine and muscles aligned...
don't be discouraged if you can't reach right away...there are quite a few stories of folks who were far away at first, but now, sometimes months or years later, they are very good autofellators
there is quite a bit of good advice on the internet these days along with lots of autofellatio or selfsucking videos too...I find them a help to get relaxed and in the mood myself too.
some good how to articles are at
and here is a book about the subject
I hope this is helpful, and let us know how you make out.
All the best,