When I began jumping, I made sure I was fully confident in my flatwork of walk, trot, and canter as well as my two point position. I also made sure I was able to do walk through canter over ground poles. There’s not really a way to tell if you’re ready. It’s really just a matter of whether you feel confident enough to try or not. As for tips, practice! If you feel nervous, bring your horse to a walk, take a deep breath, and just take a moment to calm down. You can slowly introduce jumps. I suggest asking your trainer as well! Much luck!
The half seat is used when there is not much need for leg and just have to squeeze a little to get over a relatively small jump. The light seat is also very common in the Hunter world, where you are more forward with your seat, but you are not out of the saddle like the half seat. The next would be full seat, where are sit up, and your seatbones are fully in the saddle. This seat is most commonly seen in the show jumping world and over bigger jumps. Last but not least is the driving seat. This seat is not seen very often, but is used when you need a lot of leg because the jumps are huge and you know your horse might not want to go over it. Often Grand Prix riders like Rodriguez Pessoa will do this over Liverpools and such because Let's Fly is more on the cautious side, especially with water. Now, this is all just a generalization. You jump in whatever position you are most comfortable with, or what the horse needs. Since you are just beginning, you would not need driving seat or even full seat. Your instructor would most likely tell you to get in jumping position( half seat) for your first jump. Just grab mane to make sure you won't catch the horse's mouth, and squeeze right before the jump. You should look through your horse's ears, towards an object in the distance, not towards the ground or at the jump. This is a common mistakes beginners make. Most importantly, listen to your trainer, relax, and have fun! Your style and what you prefer will come. Hope this helps:)
There are generally four seats: half-seat, light seat, full seat, and driving seat. Half seat is one of the most common, especially for small jumps and beginners, and is very common in the hunter world
You'll know when you're ready when you're confident in yourself and in your horse. Make sure you've established balance and have a good trusting connection with the horse you ride for the sake of your own confidence. Have a balanced 2-point position which you should practice often before jumping, since this will ensure you are well balanced going over a jump in the future!
Your trainer will let you know when you are ready. Grab some mane over your first jump and really squeeze with your calves. Don’t be nervous as well, ik that is easier said than done but it will go over better if you aren’t nervous. Your first jump will be really tiny usually, it really just feels like jumping the tiniest thing ever.