If you have access to a ski, try that first for about an hour or so and you will have the foil feeling.
If not, try to get up quick and early on a wave .
Do not try it on anything over knee to waist high at first.
Back foot should be somewhere on top of the mast bolts. More lift go to standing on back bolt, too much lift stay forward. More weight forward, the easier to keep it down.
Try to be on the centerline and error more to the toe side. Beginners usually get to far on their heel side and rail board over and have them fall towards the foil. If you are on toeside, it is safer when rolling over the board.
Anticipate the foil coming up and lean hard on front leg to put it back down immediately (do not wait for it to come up, anticipate it will). You want to fly it with nose pretty much parallel with water surface. Usually when first learning you will have nose to high in the air. Nose down helps the foil accelerate, nose up will stall the speed.
Bigger the wave, the more you have to keep the foil down because it will lift up harder with the speed of bigger waves
If you cannot keep foiling, try to high line up on the swell face and go down the line and not get out into the flats. This will help you get you speed up.
When you start to lose your speed , start to cut back the other way and go high line again to gain the speed back the other way.
Pumping the foil up and down will also help maintain foiling