Welcome Nuno!
1. I agree that the Mystitool works well and you don't have to attach a feather or flight band. You can get a free (or $1?) version with neat tools at their shop. Search Mystical Cookie.
2. I learned many good places by reading blogs and forums. There are some threads here that have good lists. Here's one:

3. Agree.. Ivory Tower, or find a good mentor.
From: Nino
Anyway, here are some other questions:
4- what's the advantage of seeing on SL web site who from our friends list is online? If we are in-world we can also see it... It could be better if we could send IM through SL website, don't you think?
I guess it helps to know who's online before you go signing on. I find it convenient sometimes.
Also you CAN send IM's to people inworld from offworld by using email. But only if you have received an IM first that went to email. Save that IM and reply to it...it's good for about 5 days. Sorry if this sounds confusing. I know someone else can explain it better.
5- pose balls use any prim? if I put a pose ball on a 1p pillow it will turns into a 2p pillow?
a pose ball is a prim with a script and/or animation inside it. so yes putting a poseball on a pillow will raise the count by one. There are ways to put the script and animation inside the pillow though...if it's modifiable.
6- how do I creat a wall and put a texture on one side and another on the other side?
easy.....but be careful where you click....in the edit menu you'll see a box on the tools box "edit textures" put a checkmark by that, then click the side you want to change. you should see a white "target" on the side that's selected. On the texture tab, click the texture picture and your inventory with textures available will pop up. But be careful.....click carefully hehehe. BTW--you'll have 4 other sides to texture...the edges count too.
7- any of you have ever gave a birthday party in your in-world house? did you got any cake? what have you done (I'm thinking on doing one)
I have given a birthday party for a friend. There are many shops around that sell party supplies...cakes, balloons, banners, etc. You can get some cakes that "give" a slice to whoever touches it.