It is always best to work your needlepoint on stretcher bars or in a frame. This can often be mounted in a stand, which make working your design virtually hands-free. This keep the needlepoint from stretching and warping - and keeps it cleaner since you handle it less than if you were working the canvas in your hands.
My stand of choice is a floor stand and scroll frame set made by the Frank A. Edmunds company. I like the versatility of their floors stands, as they make different types of frames that are interchangable with the stand. This is especially useful for those of us that quilt, hook rugs, and do surface embroidery in addition to needlepoint. The company also makes a handy lap frame, which is perfect for stitchers on-the-go.
Other web sites also feature quality needlepoint frames, or contains useful information about frames and how to use them.