First, it depends on what plan you have. If you have an America's Choice plan, data from the phone itself will use your minutes. Nights and Weekends are still free. If you have a Nationwide plan, data from the phone itself will cost you $1.99/MB. With a Nationwide plan, you can purchase the VCast VPak for $15 which will give you "unlimited" data from the phone itself.
With either plan, using minutes or the VPak for tethering to the VZW network (using your phone as a modem) is against the TOS. You will either need to purchase a Mobile Broadband Connect feature at $49.99/month (but you can remove/add as needed and only pay for the days you've used), or use a free dialup service like freedialup.org, which will always use your minutes, and Nights and Weekends apply here as well.
In addition, if you have a Nationwide plan, you can add a free dialup service to your Friends and Family and incur no minute usage at all.