Most important things:
1)RELAX! no tension! you only hurt yourself by being nervous, or scared! I find it helps to only look at the full bag ONCE before you get into position.
2)Choose a position before you start and stick with it. Knee-chest does give the best propagation of water through your bowel, but if you are the nervous Nelly, it may be better to use the Simms position in this case.
Whichever one you use, stay still and in position till it's time to run.
3) when you do your set up have washcloth or a hand towel in easy reach when you are in position, so that it can be readily available as a bite rag or a twist rag or at different times in the same enema, both!
4) When you make the decision to take the enema, have a "target hold time" in mind. I usually try to retain 15 minutes. Often the second round is the hardest to hold.
5) Have a digital clock positioned so you can read it without any glasses or contacts.
6) Eliminate distractions! Cell phones tablets, laptops all have off switches. don't be afraid of the off switch!
Any children or pets present should be dealt with so that they will give you at least an hour of "quiet time" during the enema.
7) Music is OK to a point, but I would keep it to a style you already listen to, so that it keeps the creative side of the brain busy so it does not keep bothering the intellectual side. Keep it mostly familiar, and not loud!
š Use a bed, sofa or cot that you have slept well on before so you are comfortable there.
9) OK to wear a knee-length nightgown or dorm shirt. or a long tee shirt. It should be machine washable in case there are any mistakes. Bra is optional, as long as it does not interfere with your breathing when you take a couple of deep breaths. NO PANTIES! they just get in the way, both during the enema itself and during expulsion.
10) Start off with just plain soapy water, WARM BUT NOT HOT!! to YOUR touch. No matter what anyone else thinks.
11) Hang the bag the right height to give you a flow rate you are comfortable with. For me it's about a quart per minute. That's fast enough that I feel it in a matter of seconds but not so fast that my body refuses retention.
12) Insert the nozzle SLOWLY and POINT IT TOWARDS YOUR NAVEL! No excuses just do it. Whatever nozzle you use, make sure to get it ALL THE WAY IN!! A flared nozzle is harder to get in, but acts as a butt plug, helping retention.
13) No hurries! I'm an experienced enema taker and I average over a session one enema per hour. This might be fast for an inexperienced user.
14) ALWAYS ALWAYS ALWAYS Take a few minutes after insertion and RELAX AS MUCH AS YOU POSSIBLY CAN!
15) Take the valve in your hand, Take at lest 3, more if you think you need them Slow, deep as you physically can breaths. Then Breathe in, open the valve, and breathe out. Let it run. Focus on staying relaxed, and in position. Let it flow!
OK to look up at the bag occasionally and see how you are doing. DON'T stare at the bag, you will only psyche yourself out! It's OK to clench up, but keep the rest of your body as relaxed as you can.
16) When you are really not sure you can hold it, twist that washcloth up, and take slow. deep breaths until the urge subsides. There will come a point where it does not quite subside all the way. This is a sign that you are getting close you might want to stick that bite rag in your mouth and be ready to bite down the moment you need to! When you can't hold it any more walk fast but don't run to the toilet. it's OK to bend over, or put your hands in the air or both. Once on the toilet just relax and let it flow OK to push a little but not hard!!!
Do these things EVERY time and you should make any realistic retention targets, without any balloon nozzles or anything weird like that.