Acrylic paint is probably the most versatile type of paint that an artist can chose to work with. Depending on how the paint is used it can easily mimic both watercolor and oil painting. Painting with acrylic involves less messy clean-up than oil painting, but still allows for opaque over-painting if the artist has a change of mind. Unlike watercolorists who need to be sure of their intentions before putting pigment to paper, acrylic artists have the luxury of knowing they can always paint over any detail they chose to alter. The combination of these factors makes acrylics a favorite choice among the more experimental and improvisationally-minded artists.
Acrylic paint can be used on a variety of surfaces, most commonly canvas, but also paper or fabric. The name acrylic comes from the medium the pigment is suspended in (as is the case with watercolors and oils). Acrylic is essentially plastic which is why dry acrylic paint often has a shiny quality to it.
Acrylic paints will not bond well with slick nonporous material like glass or metal and will easily scratch off if faced with any wear. Artist acrylic paint should never be used as a substitute for household latex paint and the reverse is true as well. Latex house paint will crack and flake if used improperly. Acrylic paint meanwhile will easily scratch off when painted over nonporous surfaces. Attempting to paint a mural on a wall coated in a glossy finish will end badly. However, other than these obvious exceptions, painting with acrylic on most surfaces works extremely well. For painting on fabric, watering down the acrylic paint will allow the pigment to soak deeply into the fabric without producing that rubbery quality that some people don't like, particularly for items to be worn as clothing.
Novice painters often avoid painting on canvas fearing the price, substituting stiff canvas board, paper, poster-board, or even cardboard. All of these will work from a painting perspective. However, when it's time to mount and display the artwork, the cost of framing non-traditional media may actually exceed the price of a simple canvas. A finished painting on canvas is lightweight and easy to hang unframed. Indeed, hanging canvases unframed has become something of a trend resulting from the modern minimalist aesthetic. Meanwhile an "economical" choice of cardboard for instance will leave the artist with a piece that now requires more complex display options and is more at-risk of damage from humidity. Not counting the proverbial blood, sweat, and tears, framing is far and away the most expensive aspect of a finished piece of work. Knowing this and planning for it, or in the case of gallery-style canvases, planning to avoid it in advance can save a lot of money and headaches later.
The number one rule when painting is the same rule that applies to all art: only the artist can say whether the artwork is right or not. If the artist wants a distressed, scarred look then cracked paint is a feature not a flaw. Some artists have gone as far as using hair dryers to force the paint to dry unevenly and warp deliberately. Hundreds of books have been written and thousands of opinions have been shared about what constitutes a successful painting, but the only real point that matters is whether or not the image on the canvas (or the cardboard) fits the original image in the artist's head.