Well, I'm not a modeling 'ace', but here are couple of things I've picked along the way. Everyone is welcomed to add their own.

So, you want to start scale modeling? Welcome! Before you begin, please note that although this is a great hobby (as each person will say about their own) some commitment is involved.

start small. Many a time I have seen people jump straight to the deep water of things, only to find that scale modeling is not their cup of tea. It can be someone who purchases all the stuff you need from top-name brands, just to find that he he doesn't like the hobby, or someone buying so much kits at once, he is out of funds to even buy glue, and just feels bad on the whole thing (true story).
So start low and small. here's how:
1)
scavenge your house for tools. you will need a sharp knife, and small scissors. get some cheap CA glue and a medium round brush.
1, a)
pick an easy model. go for 1:35 scale, as 1:72 is too small, 1:16 is expensive and I have nothing to comment about 1:48 I recommend italeri's m4a3 sherman. it has a low parts count, easy to built and the result looks good (was my starting model).
1, b)
Open the box in the shop, and buy your basic paints. these should be an over-all color, black, and perhaps gun metal. don't go for all the detail colors yet.
1, c)
Start building. don't force yourself to finish the model in a day. take your time.
1, d)
Paint your model with the paints you've purchased.
1, e)
Are you satisfied with the result? was it fun? did you enjoy it? now you can move on.
2)
When moving on in the hobby, try and keep it on the low still. go to your local hardware store, and pick some tools such as a knife and tweezers.
2, a) Pick another low parts count, easy model. this time, get all the colors you need, plus a thin brush for details - it should be 000 type of brush, but as long as it's thin, you'll be o.k
2, c)
again, build you model.
2, d)
Paint it. make sure you go for all the details this time.
2, e)
Now it's time to move on. try some basic weathering. you can search armorama for articles and missing-linx has a great section too
here
don't be tempted to try them all at once. first, familiarize with the basic techniques - washes and dry brush. articles about washes can be found here
3)
If you bare it till now, start getting your tools here and there, get some info about airbrushes and compressors and carry on
You can search armorama for articles and tips, plus ask questions.
Have fun. Hope this will help you

Matan,

Good review. The only thing I would add is to suggest avoiding PE in the first few kits.

Tony

Great Tips and Advice ! Thanks for posting this I am sure that it will aid the newcomer to the hobby. milvehfan

Another tip:
On each one of your builds, try a new technique or method that you haven't used before. This is pretty much the only way for your work to improve.

Also, have a few builds on the go at a time, so that when you tire of one, you can switch to working on another.

thanks
@Tony, yeah that's a great tip. resin and PE are a bit intimidating at start.
@milvehfan: thanks
@Scot: another good tip. I don't think that working on more then 1 model is recomended for someone who has just started. just my opinion

Hmm I must be way off base then, I think its best to jump in all at once.

Jumping in all at once ! I have seen this all to offen where an individual goes out and spends hundreds of dollars on supplies and kit's for the stash builds one model and doesn't like the hobby or they loss interest because their not getting the same results as from other modllers who have been doing this for a long time . So for some who is planning or just started into the hobby one of the best tools they have is asking questions !