I have experience with solo administration as you know probably from having read my other posts.The first thing is to find a place or time when you will be totally undisturbed for a period of about two hours. Why so long? Well you will need that amount of time for preparation, administration, expulsions in a leisurely manner, and then the inevitable clean-up.
I have tried different places - bathroom floor, tub, bedroom - all work, it is just a question of which one is the more relaxing at that particular moment. Make sure you scout out the location beforehand so as to make sure there is a hook to hang the bag and any other logistical consideratons.
Positions: I have tried several but keep coming back to knees over chest. This is a matter of personal taste; I got started in that position as a child.
Atmosphere: if you like, play some soft music and light a few candles. The candles can help dispel unwanted "fragrances".
Clean-up: not just the equipment but the room. My wife said our bathroom reeked after my latest adventure. So now I am in the market for an industrial strength room air freshener. It goes without saying that cleanliness is next to godliness in our fetish. Like it or not, we are dealing with some toxic bacteria and sanitary considerations are paramount. Be sure and clean your equipment diligently.
Equipment: I prefer a red two quart bag with a retention valve, long soft rubber tip. I lube my tip and bum up and I am ready to go. I switch between liquid soap and Ivory. The liquid leaves an oily film inside which facilitates expulsion without the mess of an oil enema.
Bulbs: See my earlier posting on monster bulbs. You have to have the hands of a body builder to make the damn things work. Personally I am not that big on bulbs, prefering to "bag it".
I hope this helps. Good luck.