I have been attempting to do this for a little over a year now? Progress is slow of course, because I have not yet mastered falling asleep conscious and dreaming, but I believe I have succeeded? I woke up before I got the chance to really do anything in my friends dreams, but I am wondering how I can tell if its a dream or not. I did try entering a different friends dream (turns out he was awake) and I felt a block. Perhaps this is proof enough? Anyway, I also came to ask about dream magic advice and if anybody else has successfully done this. Any help would be greatly appreciated, thanks!
Walking into someone else's dream is a matter of belief, and rarely do those who think they may have succeeded find confirmation from the other party, whose dream the initiator believes they entered.
Even if you do succeed, the concepts and symbolism of the other person's dream may appear completely different to you, and you would be looking at aspects of their dream from an external perspective -- not from the one which their own subconscious is working through. The other person may not appear as one would expect, and not even in a comely manner. The same can be said for the person who believes they are transiting dreams of other.
The best way to find out is to ask the other person. It is also important to have consent, as well as keeping careful notes, and arranging for the attempts to be made concurrently, rather than randomly. Nobody here could actually tell whether you succeeded; it is shared gnosis, belief, and interpretation between the participants in the exercise.