Yes, the USPS site is very helpful.
Be sure to read up on the difference between the shipping methods, and what they cost. Do as much research as you can, and communicate clearly with your customers as to what they are paying for.
IE, if you're shipping items via First Class shipping only, the packages cannot be tracked or insured. If they get lost- they're lost. Make sure you state in your policies if you replace items or cover the cost of re-shipping them.
Tracking and insurance is only available on Priority and Express methods, which are much more expensive.