Family magic effect testers
Ever since I began to practice with magic and "graduate" to the more advanced magic effects, I have always used either my Dad or my brother to test the effects I have been working on so hard to get just right. And then the great thing about it is, like others who have stated this already, it's better to get constructive criticism from your Family that your friends or strangers. Unless you have a really good, close friend, I never practiced or had shown an effect I had worked on for 2 weeks to other friends. Simply for the fact that some of them will love to call you out during your effect to make THEM sound funny and to make YOU look bad.
There has been countless times when I feel confident with an effect and I will perform it for my Dad (or brother if his in town) and he'll say, "That was really great! But when you did this, you flashed that, blah blah" and basically tells me how much further down to display something, or work on a move that looks to awkward.
So I am very glad that I have a family that supports me 100% of the way and also encourages me when I am having a difficult time with an effect.
There was also this other magician who told me that since he didn't have any living parents or siblings, he would set up is Camcorder and then video tape himself performing, then move in a different direction and perform it from a different angle. Which I also think is a great idea, if you don't have someone in the room to give you live feed back, but of course watching yourself perform and messing up, is just as good as having someone in the room with you.