Step 1 Recognize that every horse is different

A more willing horse can certainly help while riding cross country.

Step 2 Gauge the start according to how fit your horse is

For example, if your horse is not overly fit you don't want to be going bull at a gate, since this will mean your horse feels 'energy sapped' towards the last fences. This can be dangerous.

Step 3 Learn pacing, another important aspect

Pacing is very hard to teach, as again it depends on your horse. Aim for a pace that your horse is comfortable with. Often this is more of a quicker canter rather than a gallop. Aim to help your horse into a nice 'rolling' pace. Strides should be longer than your average 17ft canter stride, but to the point. The back legs should be engaged, not trailing along behind.

Step 4 Look at the fences

There are many many different type of cross country fences. Some fences will require you to set the horse up. Others, such as hedges and palisades can be jumped more often than not out of your current stride.

Water Fences. These don't appear on all courses, but should be trested with caution. Make sure you check the depth and footing EVERYWHERE when walking the course. Just in case the worst should happen, you need to make sure it's safe. You will need a lot of energy when approaching a water fence, so aim to get the horse/pony back on their hocks a little, also make sure you sit very defensively - you don't want to take a dunk!
Ditches - These tend to cause problems! If your horse doesn't like ditches, practice, practice, practice! As the rider, don't look into the ditch. Usually the horse is in tune with your motions and will also look at the ditch!
Benches and Table - These are shaped like solid picnic tables and benches, and many horses will spook at these objects. Take care when going over, and never approach it from the wrong side.
Corner jumps - These are shaped like an open triangle, and should be approached at the narrowest end.
Roll tops - These jumps have a big 'spook' factor. They are quite wide and long, so should only be approached by experienced riders.
Drop fence - These can lead to a drop onto ground or water. These are very hard to jump, and should only be approached by experienced horses and riders, with someone watching, due to the fact that there is little way of 'spooking' without someone or something getting hurt. For this riders should lean back when in midair in preperation for the fall below, with the heels down to absord shock. Allow the horse lots of rein.

Step 5

Skinnies - These are very narrow jumps, designed to challenge the rider. These can be difficult to get over due to their small size, and whether the horse is co-operative or not.
Pheasant feeder - This jump is a tricky jump, and it looks like an elongated roof. Because both sides are stretched out, horses can easily misjudge landing positions, so much care should be taken.
Tyre jumps - These are simply lots of tyres staked against each other around a long pole. These are generally small, but exciting and spooky to jump.
Spreads - These are jumps consisting of several poles or logs placed near each other, gradually getting higher. These are difficult to jump, and should ONLY be approached from the side where the smallest pole starts.
Simple jumps - These range from simple logs, to verticals, to fences, to bushes. The easiest to jump, and can also be the most exciting.
Novelty jumps - These can cause even the safest horse to spook, as they can be shaped like 'scary' objects such as: Houses, Mushrooms, Haycarts, Stables and more. These can be wide or long, big or little, but should be jumped with care.

Step 6

Owlholes - These can be some of the most tricky jumps on a course. They appear on courses less often, and are shaped as big hedges or fences with a wide hole in the middle. These can vary in size, but are extremely difficult to jump due to being very high on a horses spook factor. They will usually be at the end or beginning of a course, and should only be attemted if your horse is reliable, safe, you are confident, and there is someone there supervising.

Tips

Don't attempt jumps your horse is not capable of, know what your limit is.
Approach at a steady but fast canter, with more speed for larger and harder jumps.
Never force a horse to do a jump, but try to 'teach' it gradually.
Have someone around to help you.
DON'T look down.

Warnings

Always walk the course, especially if you have not seen the course before. You wouldn't want to get there and have an accident.
Stop when your horse is tired. Use good judgment. A little bit tired isn't bad, but if you feel your horse is struggling (particularly towards the end) make sure you retire. This is something that almost ALWAYS ends in a horse fall which can be potentially fatal, so if it's too strenuous, save it for another day.
Only approach difficult and tiring jumps if you and your horse are confident and ready.

Via wikihow