So you are on a lineup. Turned back to waves and decided to catch the next one. Here is one of the techniques to stand up on a longboard.
Start to paddle in order to get a speed by the moment the wave comes to you. As it happens paddle two, three or more extra strokes to force your board down the wave face.
Then you become on top of the wave and feel its speed, place your hands flat by your Ribs/chest and your toes on their toe tips — ready to spring!
Push off the board. Hips and bum up, take one small step with your back foot immediately followed by a bigger step by the front foot – aimed to land in the middle/centre of the board. Usually in-between your hands& Make sure that you are looking up and in the direction that you want to go. Keep low in your stance, stay firm on your feet and tuck your back knee behind the from knee.
Lift your hands up to chest level for extra balance and control you surfboard sliding to the beach.