Guides. Really. Otherwise, get used to the usual motions usually found in arcade games, such as quarter circles, half circles, 360 rotation. It all depends on the game and character, too. Some characters have moves where you have to hold back, then foward + Button. When trying to get into it at first, it does look daunting trying to remember this stuff but you soon find which characters you click with and which ones to avoid.
And practice at home. It may be hard to transition from joy stick to controller or vice versa, but at least knowing what to do going in gives you something to work with when readjusting. Luckily, most fighting games don't change up too many moves, if any, in the sequel, so you should be good to go if you try an older game