Can someone give some tips on this for a first-time farang visitor?

My tip for a 1st-time visitor: don't.

The art of the proper wai -- an art that I do not profess to know well -- is complex. In a proper wai, the height at which you hold your hands, the depth of your bow, and other body language will depend hugely on the person to whom you offer the wai and his/her societal relationship to you. A Westerner would surely need to spend years in Thai society to understand it all.

So, if you attempt a wai, the overwhelming likelihood is that you will get some of it wrong. Not that anyone is likely to be offended -- you, as a Westerner, are not expected to do things the proper way. But neither will you impress anyone with your knowledge of local custom.

Far better, in my experience, to smile and nod your head slightly/slowly, or offer a handshake if appropriate.

The basic rule is that when you greet someone with a "wai" and if the other person is older than you then you will have to be the one to do it first. If someone give you a wai then return it immediately.

I've found this local website and I think it's quite useful if you want to know more about wai:

http://www.sriwittayapaknam.ac.th/thaiculture_1.html

And from the same school a short video instruction on wai for children:

http://www.schoolvideoblogs.com/scho...-to-wai-2.html

On the video, when the girls bend their knees and wai, is that type of wai from children to like a grandparent? The only part that i understood was 1,2,3 wai and i am happy i got that! tomorrow i can have my thai friend interpret it for me, but tonight its too late to ask him to come over.

That's the most polite way for a women, or girl, to wai an older person or someone of high standings. Normally use for someone of high respect like from a student to their teacher.

If someone greet you with a wai, and you're a women, you don't need to reciprocate with that type of wai just a normal wai will do.

This etiquette is something that Thai people learn from an early age to it becomes much more of a simple 'instinct' than something to 'think about'.
After so many years you can still easily get it wrong, as others have said it depends on age/status etc, and of course that can change from meeting people say in one room and then moving to another room.

I go with the view that you are not expected to get it perfect, I honestly would not worry too much, a Thai will guide you but in many cases you do usualy simply do not have any time to 'think', that is where instinct comes in, and you don't really have much time to think about it.

Your Thai friend will tell you the basics and leave it at that, I would not worry too much. A quiet, smiling, respectful and pleasant demeanour(sp) for sure, and that really can apply anywhere.