Make a scale plan of your garden (preferably on graph paper) and make several photocopies of the plan. Use these to draw out various arrangements within the designated area. You could use concrete paving bricks, but it is easier and quicker to lay larger square or rectangular paving slabs. Make less work for yourself by planning to use whole slabs wherever possible - adjust your plan to suit the size and shape of your chosen paving in order to minimise cutting. Paved areas often seem very different when plotted out life-size - before you make any firm decisions, lay out your plan on the ground using lengths of string. The type of foundation you need to lay is determined by how you intend to use the patio:
A walkway for occasional use can be laid directly onto a base of sharp sand. A patio is best laid on pads of sand-and-cement mortar placed on compacted sand over a sub-base of broken-brick hardcore.
Excavations result in a surprising amount of soil - if you can't have it carried away, use the soil to construct a rockery elsewhere. You may have to excavate the ground so that your new patio remains at least 150mm (6") below the damp-proof course (DPC) in the house walls. Check whether you need to cut slabs to fit around drainage gullies and manhole covers - if possible, rearrange the slabs to avoid unnecessary cutting. Do you want to incorporate outdoor lighting? If so, it may be best to have cables run before you lay the patio.