How to join a Steam gift group?

1º you have to kill a dragon
2º you have to recover the stone of sacred tears (probably you would have to killing another dragon)
3º you have to be lvl 42
4º ???
5º you have to become a dragon (that means killing a lot of dragons)

After the owner of the group sended an invite,you get a notification then you click join.

From this guide

Private group giveaways

These groups are much more difficult to join, as they will often have certain requirements you must meet, however they will also have high odds compared to public giveaways. Common requirements to join such groups include

• Being active in the SteamGifts forums
• Having a certain amount of contribution value
• Making regular giveaways within the group

Offer the leader sexual favors. Works every time.

suck my 7"

straw which I just put in a smoothie and tell me how it tastes. Then I will send you an invite to my uber pribave group (I'm obviously trolling, pay attention to what Delta said)

I wouldn't hold my breath with profile stats like that, though.

And what are you planning to do when you join one?

If you have to ask before coming to the conclusion of being social in the community I think you can expect a bit of a small challenge but pretty much easy if you follow the guide below that Delta linked.