Hi, my pony (Shelly) is a very good natured pony. She only has one little issue that needs to be corrected. I take her out on rides regularly. When I instruct her to go ahead and walk she does not go. The only way she will move while you are on her back is if someone else is leading her with a lead rope. Other than that she is a very good pony and if I can correct her and get her to walk while I am riding her I would be so happy.
I think some additional details would get you some quality answers :)
1) how long have you had the pony?
2) Is this a recent development or a "from day one" issue?
3) what aids have you tried?
I'm sure there are more details that would help too...
In addition to LauraJo's great questions -- How old is the pony? When was she last vetted? What is your size in comparison to the pony's? Is she like this with everyone or just you? What is her history of use (ie a "pony ride" pony or not?)
Ponies are smart and quickly become very good at outsmarting people. Repetitive tapping, not on the rump, but behind your leg where your arm hangs straight down should elicit a response. Sometimes they will pop forward for the first stride so be very careful to not accidently pull on her mouth. If you tap her on the rump this seems to elicit a buck which you don't want. By tapping her, think of an annoying kid brother tapping your arm for attention and won't let you ignore it. He gets your attention, right? It doesn't hurt, just annoys and that's what you want to do with the pony. Be sure to stop tapping the moment she's moving forward. Be patient and don't quit until she moves or you've reinforced her behaviour. It might take a minute or ten minutes or more.