what kind of things do you look for to see if they are in trance.
I heard others using:

1. flutter eye lids
2. change in body temp
3. Arm drops, speed and limpness
4. eyes roll back.
5. Body goes limp and seigh comes out.

what are some you look for?

I recently presented the effect from Necromancer's excellent Xpert where you have an out of body experience, removing an initialled coin from the participant's hand and placing it in their pocket in the process.

I start this routine by having the participant "hypnotize" me via maintaining eye contact and counting backwards from 10 to 0. The person who did this most recently is certified as a hypnotist, has a doctorate in psychology, is well versed in Erickson's methods and had used hypnosis in his practice before he became a professor.

The next day he called me and said that the one thing that let him know I was in a real trance, was the way my eyes fluttered when he was at about 4 in his countdown. He didn't believe that this could be faked. I am proficient in self-hypnosis, so in one sense I wasn't totally faking. I mention this to give you an idea of what an academicaly trained hynoptherapist looks for and also because I got a kick out of his take on what had transpired.

There are many "minimum cues" that let you know someone is in a trance. Being able to determine how deep or what stage is another thing that only comes with practice...

The worst part of a show for a stage hypnotist is when he gives the first commands to his subjects. If they follow the rest of the evening is easy money! If they don't...

And sometimes its near impossible to tell. Trance state is also very unstable at times.I would also say stage trance may be different from theraputic trance.

Any body movement of the spectator can be relabeled ad-hoc as a supposed effect of the state of trance

Some visible signs of trance (in addition to those already mentioned:

(1) Extraordinary stillness of the facial muscles.

(2) Face becomes noticably paler (this is true whatever the subject's ethnic group).

(3) Breathing becomes slower and deeper.

(4) Swallow mechanism is either reduced or stops.

(5) Circulation of blood slows (this can be observed if you can see the subject's pulse and is confirmed when the subject on awakening experiences "pins and needles" in the hands and feet.)

(6) Any body movements are usually slow and sluggish.

(7) Any speech is usually slower and characterised by "literalness" (e.g. When asked, "Do you know your phone number?", the subject would reply "Yes", rather than actually giving the number.)

That is true experience is the only way to know. (most of the time)..