Seeing as you're an Aussie, I'll assume you're riding in an English saddle. Two ways - either get a leg up from someone, or mount from the ground. However, mounting from the ground isn't great on the saddle, stirrup leather or your horse's back so try only to do it when mounting from a block or getting a leg up isn't an option. Good thing to know if you're out on the trail though, nothing more annoying than having to get off to pick something up that you've dropped (glove, phone, water bottle or whatever) and not being able to get back on til you find a log or wall!
1. Make sure the girth is done up nice and tight - you don't want the saddle slipping. Test for any movement by putting your weight in the stirrup with your hand - really press into it for a few seconds and see if you can feel any slipping.
2. Do a few leg stretches. Pull your foot up behind you til it touches your butt cheek. It makes a massive difference in the reach your leg will have.
3. Make sure your foot can reach the stirrup. It might be a bit of a stretch, but if it's too far, then drop the stirrup down as long as you can - I usually don't drop down past the 2nd last hole however. Don't put your foot in just yet, however.
4. Take the nearside rein (the one closest to you) and hold it in your left hand at the top of the wither, with the horse's head turned slightly toward your side. Grab a bit of mane and wither as well. This will give you control.
5. Place your foot in the stirrup. With your right hand, grab the cantle (back of the saddle) and swing up, making sure you don't kick him with your right foot as it swings over his hindquarters, and that you don't toe him with your left foot. And you're up.
6. If you needed to adjust your stirrup length to get up, with reins secure in one hand (not looped around your arm) take your left foot out of the stirrup and lay your leg slightly behind
the line of your stirrup (this will allow you to still have a secure seat). Feel under the jockey (small flap) for the stirrup buckle. Undo the buckle and place your foot in the stirrup. Take the leather up a few holes until it feels even with the other stirrup. You may need to adjust and check a few times. Finally, run the buckle up to the top of the stirrup bar and put the end of the stirrup leather back in its keeper.
Parts of a saddle: English saddle - Wikipedia, the free encyclopedia