Hi mitecoach
This is a great question and it raises the big difference between "teaching stealing" and just having your runners move from 1st to 2nd and 2nd to 3rd during a game.
At the mite level - you won't see a lot of throws from the backcatcher to 2nd or 3rd during the first half of the season. As the season progresses, some backcatchers will get better and we begin to see some plays on steals, especially at 3rd base.
This results in stealing being relatively "easy" during a game. Our responsibilities as coaches is to ensure that players are taught to steal properly. While a proper steal might not be important now - it sure will be towards the end of the season, and when they reach Squirt.
So, how do we teach stealing?
There are 3 components to the steal:
1) Positioning at bag pre-pitch
2) The run to the bag
3) Approaching the bag
We can break this down into distinct skills and areas for practicing/teaching.
Positioning at Bag Pre-Pitch1) When a player is standing on the bag, we want to ensure they are positioned for an "explosive" leadoff, and are also leaving the bag at the right time (when the ball comes out of the pitchers hand). To accomplish this, we will teach the players to place their left foot up against the right side of the bag. So, not ON the bag but on the SIDE, still touching the bag. The left foot should be positioned as close to the corner closest to the next base as possible.

2) As the pitcher goes into their windup, the runner should rock back slightly, getting their weight onto their back foot, and then as the pitch leaves the pitcher's hand, push off the back foot and begin sprinting towards the next bag.
Practice tips: At practice, simply have the players work on their footwork and leadoff at a bag.
Note: The reason we want the runner's right foot back behind them as the lead foot, is that this gives the runner a bit of "leeway" if they leave early. Because they need to start running with their right foot, they get a full stride in with their right leg before their left foot even leaves the bag.
Running to the Bag1) It is obviously important that players are taught to sprint to the bag, running as fast as they can. We work on running a lot with our team, as it is a critical part of the game.
2) One tendency that you will see a LOT at mites is they will look over their shoulder to home to see where the ball is. This is not what we want to happen during a steal. On a steal (at the mite level), the runner leaves the bag and should look only at the bag they are running to. Looking anywhere else simply slows them down.
Practice tips: A good drill to work on at practice for this is to have the players practice stealing (so, from their stance on the base, stealing 2nd or 3rd) - and time them with a stopwatch to see how long it takes them to steal. They can compete against their own time to try and improve. Another thing you can do which gives immediate feedback, is have them steal a bag while looking over their shoulder to home plate the ENTIRE RUN. Then time them with them looking at the bag they are stealing. They will immediately see the differene as it should be at least a second or two.
Approaching the Bag1) At the mite level, it is important (more from a safety perspective than a strategic one) that all players learn how to slide. This is what needs to be worked on as far as approaching the bag - a proper slide. Several mite teams (including mine when we were at the mite level) have had "team rules" (note: this is NOT a CMSA or AASA requirement) that declared that all players must slide at 2nd, 3rd and Home on a steal. This is not a bad idea as it helps the players learn to slide in a game situation, and it makes things safer.
2) So how to teach them how to slide? There are a few steps.
a) Have the players walk at a normal, casual pace at practice. Then clap your hands at which point they need to sit down cross-legged. The leg that they naturally tuck underneath their other leg when sitting cross-legged will likely be the one they are more comfortable sliding on.
b) Once this is determined, we need to know the correct approach to sliding. A player will kick their lead foot outwards towards the bag to initiate the slide. They will then tuck the foot of the other leg underneath the lead leg. They will start sliding on this part of their leg, then will slide down onto their bum, and will finish by laying back COMPLETELY FLAT, with their heads stretched out behind them and their head tucked in against their chest.
Video: This is a great video showing the proper form and gives a quick way to teach the skill.
http://www.youtube.com/watch?v=rPAJiSWA8rMc) So now that's the technique - and the easiest way to teach this is a slight modification of what's shown in the video. What we will do is have two parents/coaches hold a hockey stick. Players will approach the stick, grab it, and swing themselves forward, kicking their lead foot out, tucking the other foot under the knee, then sliding on the bum with their hands naturally stretched out behind them as they finish the slide and let go of the hockey stick.
So, as you can see - "How do I teach stealing" is actually asking "How do I teach a proper leadoff, correct running technique, and correct sliding technique?"
I hope this helps.