OK, The first thing is, what shall we paint?
Two approaches here
1) Find something that "inspires" us – Marc Delassio noted on his blog http://www.marcdalessio.com/ that he's spent hours driving looking for a scene. Toutounov http://www.toutounov.fr/ says you have to be excited about what you're going to paint and, likewise, notes that he drove 100 km until he found a pair of gates that he wanted to paint. Personally, I'm like this – I love it when I find something I really want to paint (though sometimes this doesn't turn out to make a good painting and sometimes an unpromising subject turns out to be great!)
2) "Its what you carry to an object that counts" (Andrew Wyeth) - Karin Jurick's http://karinjurick.blogspot.com/ motto. Here, the concept is that anything is worth painting - it's how YOU see it that matters - and as the subject of any painting is really the light (painting is the study of light) – this makes sense, especially if you want to practice a regular discipline – the idea of e.g. a daily painting – and Foster Caddell and others strongly recommend still life paintings for skills building. I feel that if I did do regular paintings I'd want to vary the subject matter – and even try and vary my style.
Now, when I painted pre 1993 (!), I was representational in that I took the drawing from life, BUT, I then tried to interpret it in terms of color, brushwork etc. - the reality was just a jumping-off point. This time round I was quickly instructed that you need to very carefully scrutinize the reality (especially for values, colour and light effects), that only with experience can you "make it up" (in fact, do it from memory/past experience) or "play with it". I got so used to this idea of observing "reality closely as master", that it came as something of a shock to realize that this was true for values, light, etc. but not for composition, content, etc. Foster Caddell has a really good section in his book where he demonstrates how he rearranges and modifies a scene to make it his own - this, of course, means that you are much less limited in your choice of subject - a subject can be vastly improved by judicious modification and editing. Here, I need some pictures to illustrate my ramblings - not enough time, just now
(Note; If you're just starting, check out the Carder method - Mark Carder sure seems to be a nice guy and just visiting his website and looking at his free videos presenting his method and reading about it tells you everything - you don't even need to buy it! Some people tried to pooh-pooh him - another "magic" method, but some serious guys said it's sound - and I agree - I didn't buy it - but found it very instructive and inspirational)
OK, so we have a subject (wish I did!) now we need the materials acrylics/oils/watercolours - which gives me the chance to speak about most painters' favourite subject - palettes (I'll keep it to acrylics/oils) and a support - rigid (gesso on panel/canvas on panel) or flexible - canvas. Personally I now always tint my ground with a light wash of burnt sienna - gives a pinkish/orange-ish colour (reasons for this another time)