From the kind people at oilpaintingsguide.com (second part to come next week) -

Acrylic Painting Tip 1: Keeping Acrylic Paints Workable

Acrylics dry much faster than oils so my advice is to squeeze only a little paint out of a tube at a time. Also take a look at the palette you are using. Some have a waxy finish to them. These are ideal as they will not absorb moisture at of the paint. Alternatively, frequently flick water from your brush on to the lump of paint. In a dry climate the paints will start to set within 20 minutes of being squeezed out from the tube.

Acrylic Painting Tip 2: Blot your Brushes

Keep to hand tissue paper or a towel. Remember to blot the excess water from your brushes before you apply to canvas. Otherwise, you’ll have water running from the bristles down on to the canvas in messy streaks. Blot your brushes or pay the consequences!

Acrylic Painting Tip 3: Opaque or Transparent

Depending on how you apply the paint acrylics can be either opaque or transparent. Apply thickly from the tube and mixed with a little white. If diluted down with water the acrylics will appear in essence, much like watercolors with a similar effect.

Acrylic Painting Tip 4: Acrylic vs Watercolour Washes and Oils.

Once acrylic paint dries that is it! Unlike working with oil paints, you can not re-work an area of the canvas hours later and, unlike watercolors, acrylic paint is totally insoluble. If you have made a mistake, all is not lost! You can paint a new layer over the top.