Palette set-up
The set-up above shows a palette with paint and brushes, a wet sponge (for blotting brush as needed), a large water container, and paper towels.  
It is good to get a sturdy plastic palette with cover.  The cover helps keep your paints moist inbetween sessions, serves as an extra mixing area, and is convenient for transporting. 

The pure tube paints are squirted and stored in the outer wells of the palette.  You then pick up pure paint on your brush and mix in central mixing area, adding water to get the consistency you want.  More water will lighten the value. 

It helps to spray the paints with water occasionally inbetween sessions to  keep them from drying out.  Also you might want to spray them 15-20 minutes before a painting session so that they will be moist when you begin to paint..

To start out, you can do well with 3-4  brushes: 1-2 medium or large round brushes, one 1" flat brush, and 1 rigger or liner brush (for detail). 

Paper set-up
Watercolor paper comes in hot press (smooth surface), rough (rough surface) and cold press  (inbetween smooth and rough).  I recommend that you begin with good quality 140# cold press paper.  It helps to tape your watercolor paper  to a sturdy backing board.  (Some artists will use bulldog clips instead, or just paint with the paper loose, but this is more challenging.)   For tape you can use artist tape (or masking tape in a pinch).  For a board, you can use plexiglass or coated masonite board.  I like to use "tile board," which is masonite with a white waterproof coating on one side.

It usually helps to keep your board at a slant (I use a block of wood to prop up my board).  This way gravity helps you--for example as you apply a uniform wash, you usually go from top to bottom.  When the board is slanted you always know that the wet edge will be the bottom edge of a brushstroke.

In the above image you also see a water spray bottle and a box of tissue, both very helpful in your work area. Besides using  water from your water container, you can use the spray bottle to add water to your paint mixtures.