Yeah start small and work up. Also if there is a table (flat part between jump and landing) speed is your friend. There is no better way, outside the half pipe, to jack your self up than coming up short on a jump. Seriously, if your mountain has properly built jumps it's pretty hard to seriously hurt yourself provided you make the landing. I have landed on my side/back with no feet hitting and it certainly doesn't feel good but you walk away with a bruise. I stressed fractured my foot coming up short on a 25 footer and have seen multiple people carted off after hitting the knuckle.
Starting off your going to feel like your going mach 5 into a jump only to barely clear the landing. Don't be afraid to ask questions most people are more than happy to give you pointers. Contrary to their rep most people in the park are super friendly and are excited to see everyone progressing whether it's your first air, first 360 or landing double corked. When I first learned to spin a 3 I had guy come up an tell me that was awesome. Latter in the day I saw the guy throwing 9s and rodeos.
BTW the size of jumps is measured by the length of the table