It's short for "What are you..."

I think when I use it, it comes out more as "Whatchu(oo)"....as in "What you doing?" 

Whatcha is more like "What ya doing?" which has a more playful and childlike sense to it. I would say "ya" instead of you....when I'm being more playful or speaking to my daughter, or being cute with my boyfriend. Maybe it's just me.

I wouldn't make a point to force the usage....it kind of comes just from shortening and slurring words together. No one would consider it part of their vocabulary. 

"What are you doing?" is far more common....and perfectly fine.

I do a mixture of both. I found it boring to start speaking when I could only say basics. I couldn't even understand enough to have someone explain something to me. So I turned my focus to explanding my vocabulary and listening skills. I think listening is super important. Whats the point of being able to say a few things only to have to constantly ask people to slow down or repeat things. It gets tiring for the language partner I think. It's better now, because since I can read a bit and understand grammar...so if all else fails they can type words so I can understand. 

Now, I can read a bit (I learn kanji with vocabulary), my listening is fine....if I don't know what my partner is saying, its because I just don't know a word. But I can pick out the sounds and look it up. So basically it's good to start speaking...but it won't do you much good if your comprehension is low. Plus I can understand way more Japanese than I can actually speak, so I can watch videos in Japanese which has added a more entertaining element to my learning. If you're in a situation where you can take your time learning....I would learn voacbulary/grammar/ and listening....and practice speaking sometimes once you kind of understand....

Hiragana and Katakana first for sure.

You definitely want to listen to as uch Japanese as possible, just to get use to the language. Also the more variety of things you listen to the better, because you will have things to reference in you rmind as you learn vocabulary and grammar. 

I like this site alot, it's like drills and flashcards and it has alot of lessons. There is a section for hiragana and katakana, which is neccessary before you start vocabulary (this site does not use romanji). http://japaneseclass.jp/feeds

I use a ton of youtube sites as well to help me learn.

I like the Michel Thomas method videos on youtube from Japan Society (its like 10 hours) but its free. My brother just started learning Japanese like two days ago, and it's really helping him understand things at a tolerable way. He can even say a few phrases already.  Good Luck! 

Soap, dirt, baby powder, and erasers. Lol, embarrassing!

Sign me up! I need to practice. :)

Hiragana can be learned fairly fast, but you will have to focus on just that and use it. If you're a beginner, you should put Kanji off for now until you know the basic kana. It's really memorization. So take a step back and slow down if it's frustratng you. 

This site can help: http://japaneseclass.jp/feeds

 I've found the best way to learn kanji is by learning it with vocabulary. Then I'm killing two birds with one stone. Also it helps me guess the meaning of some words, because I am beginning ot understand what some Kanji mean. SO even if I don't know the Japanese pronunciation, I can pretty much gather what it means.