Try using techniques you've learned in the media. In one of my lucids, for instance, I took off the Neo way: Sending a pulse through the earth that propelled me straight up. In another two (or more) lucids, I used the Mario 64 way: hop once, twice, three times and you're soaring!

The second technique did have a unique after effect: a mix between the wing cap tune and star road tune from the 64 games began playing!

I suggest starting from the ground up, rather than jumping off of somewhere high. Without proper confidence, your dream could end prematurely!

Also, try asking a dream character for help. Aside from a few rude/stubborn chaps I've encountered, most DCs will do/say what you want.