It all depends on whether or not the piece you are painting has a wood grain effect moulded in.
If yes:
paint the piece an overall light wood colour, then follow up with a medium-strength wash of dark brown, and once dry, follow with an overall VERY thin wash of black. Once fully dry, drybrush first with your base colour, then with a lightened version.
If your piece does not have wood grain moulded in, consider scribing it in.
If not ,then paint the overall piece a darker wood colour. With a fine brush, take one or two lighter shades, one very noticeably lighter than the basecoat, and draw in some very fne lines, all in the same direction, following the direction that the real piece would have been cut in.