OK, there you are, standing at the top of the ramp (which I hope is no more than three feet high for your first drop--I started on one that was only two feet high). There you are shaking in your skate shoes with your board extended over the edge. You feel like you're about to walk the plank. You take a big breath, lots of big breaths.
The person spotting you should be just below and to the side of you (on the side you're facing---if you're goofy foot, he/she should be down to your left). The spotter--standing as far away from your intended path as possible while being close enough to hold your hands--reaches up and offers you their hands. You lock eyes, your spotter calmly and patiently reminds you of what you need to do. When you're ready (ha) take a deep breath and in one fell swoop slam that front foot onto the sweet spot of your board while leaning forward. Your spotter should point this spot out. I know people who have actually marked it with an X in chalk.
Leaning forward doesn't mean throwing yourself over the side head-first. I think someone described it to me as "leaning with your forward shoulder, then following with the rest of your body." Also remember to bend knees slightly as that helps absorb the shock of the drop and stabilizes you as you roll.
A few notes on using a spotter: You don't want to have a death grip on the person's hands because when you drop you don't want to be hanging onto your spotter (granted this is preferable to a face slam). It's really just for a bit of stability and more than anything moral support.
A tall strong person is great because it gives you some semblance of confidence that if things go awry, this person is there to diffuse your fall a little bit. I suggest the spotter be as heavily padded as the dropper! Not everyone is helped by this--some might even be deterred by this--but it made a world of difference for me.
I think it's also important to have a spotter who has done it themselves, otherwise the confidence won't be there, and that will make you even less confident. Spouses are often helpless at this--especially the non-skating ones--though I have witnessed exceptions.
TIPS ON DROPPING IN
1. Stay as low as possible in relation to your board. This limits the pain; the closer you are to the ground, the less slamage (technical term for ya) you will experience. So bend those knees!
2. Start on banks or very shallow mini ramps and work your way up. Get the feel of transferring your weight forward and rolling away from each height.
3. Think about pumping the transition below you, not "dropping." If you focus on the pumping down, your balance and drop-in will be a natural start to your run. If you simply "free fall" onto your board, you will not have your balance until you stop the free fall. Focus on pumping down the transition, just as if you did a kick turn as high as you are when you're starting your drop. This is especially important when dropping in on vert. Notice when a person kick turns on vert they squat or bend their knees naturally. This helps when dropping in too.
4. Think of dropping or pumping down--not out. It's a subtle difference, but all too often I've seen people learning and they try to drop out and end up off balance on the way down. In essence, your rotating your center of gravity and letting it go downward. You don't have to project it out.
5. Don't lean back. The instinct is to try and slow down, and leaning back is a fail safe. Unfortunately this leads to a bad slam. Once you decide to go, don't hold back. Stay over the board and hang on if you must, but don't lean back.
6. Pad up to the hilt and have a spotter if possible.