Although I am also still learning, what has helped me is the following:
1. Practice! The more exams I've done, the easier it has gotten.
2. If you can see just a part of the cervix, pull halfway out and reposition.
3. I personally started out with a tendency to aim too anterior. Often I had to reposition and aim more for the sacrum.
4. Don't open the speculum until you are all the way in.
5. If all else fails (and it's safe to do so), remove the speculum and do the bimanual first. Sometimes when you feel where things are, it's easier to get the speculum in right.
Hope that helps!