A few thoughts:
1) Get contract provisions in writing, engage a forester, and get a cruise done so you know what your inventory looks like.
2) Make clear your expectations for placement and repair of roads, creek/ditch crossings, waterbars/turnouts, etc.
3) Not sure what kind of timber you've got but for pine, slash redistribution from the decks back into the residual stand is important.
4) If you have multiple products (pulpwood, chip n saw, sawtimber, veneer, poles etc) the knuckleboom operator is the most important man on the job. Properly sorted wood maximizes revenue and working with your forester, merchandising/marketing is key.
5) If it's a thinning job consider penalties for damaging the residual stand through careless felling, skidding.
Good luck with your harvest!