Like Annabella said, work on your flat work before hand. Get your horse focused on you. Do lots of transitions and leg yields. Reward your horse with a pat when he/she does what you want. After that I wouldn't work on grid work so the horse learns that he/she has to be slow to get through it, then halt after. I hope this helps!
Hi! I would work on your flat work before hand. Do a ton of canter and walk transitions and lengthening/shortening their stride. The first couple jumps try halting afterwards. Pole work with halting inbetween etc.