First off I'll go into explaining a miszou for people who don't know what a miszou is. A miszou is when your front foot is sliding on it's soul and your back foot is turned and sliding in the groove between the 2 and 3 wheel. This trick can be done on curbs, planters, rails, ramps, or whatever you can find to grind on.
How to miszou a curb/ledge: Approach and jump just like you are going to pull a backside grind, but instead turn your front foot so that it's on the soul and is pointing where you want to go. As you gain experience, you will become more fluid with the trick and won't have to think about doing a backside, but simply jump up, bend your front knee and land soul on your front foot. But until then, try and keep a few key points in mind. Make sure to keep your body facing the direction you are going. Also keep your front knee bent(boned) so it's leaning into the thing you are grinding and keep your weight centered on top of the ledge. Play around with your weight distribution until you feel comfortable, but most of your weight should be forward, and on your front foot.
How to miszou a rail: A miszou on a rail is very similar to doing a miszou on a curb, but on a rail you can bone your leg over more, but ALWAYS keep DIRECTLY on top of the rail or you will lean off the rail (or fall). I think it is easier doing farsides miszous on rails, but that is just my preference. Either way, you MUST make yourself get on top of the rail or you will fall.
Notes:Make sure whatever you are grinding slides decent or you will pull a superman and/or bust a nut. I think miszous are easier than souls to learn. On a miszou it is easier because you can watch your soul foot since it is in the front of you. (And that is where all your weight goes).
Advanced miszou Tricks on Planters/Rails:
Farside miszou-jump like you are frontsiding, but turn your front foot so it lands soul. Halfcab 2 miszou- This is a hard trick to learn, but once you get it, it'll be one of your favorite tricks. Approach the planter/rail backwards, jump 180 and land in miszou stance on the planter/rail. You can either jump into/or out. Jumping in requires more spinning and jumping out you simply turn your outside foot 180 and your inside 90 and land the trick. Other great miszou tricks: Alley-oop miszou, sweatstance(top side miszou), kind grind, halfcab to farside miszou, disaster miszou, etc.