These rulings helped to handle odd situations, whenever they arose. These rules are superseded by Pathfinder in our next campaign.
If your mind is placed into another person's body, the following rules will determine the skills available to you:
Casting fly on a creature that already had fly cast upon it will act like the two fly spells are overlapping and the time will be extended. For example, if fly lasts for 10 minutes and you get it cast upon yourself twice at the same time, then you get to fly for 10 minutes. If you get fly cast upon you 5 minutes into the spell's duration, then you are allowed to fly for a total of 15 minutes. By casting this at the end of the spell, you could fly for an indefinate period of time.
This also applies to other spells, like shrink item. Essentially, the spells "stack", and as long as one is active, the spell effect is active.
Using any variant of teleport that lets you teleport yourself and optionally your equipment, you decide what goes with you. If you choose for another person to go with you, that other person decides what objects go with him/her. For instance, you are in a classroom with your pal and 10 kids, all of which are touching you. You decide to teleport your pal and yourself out. All of your clothing and items go with you, and your pal would probably decide to teleport with all of his possessions.
If you are bound, you can teleport to escape the binding. Same goes for people that teleport with you. However, since each person decides what goes with them, it is an individual choice. If you and your pal are tied up with the same rope and you decide to teleport yourself out, you would likely choose to not take the rope with you. If you teleport out with your pal, and he (for some dumb reason) decided to teleport with the rope, you both would remain tied up but in a new location.