You should decide if you will just be making calls in your 'local calling area' (your state and perhaps some adjacent states) or if you possibly will use the phone when you travel around the country. It is possible to switch plans, although this will sometimes restart the clock on the 2 years.
Verizon has some plans where you can add phones for other family members for a small additional charge. Family members can then talk to each other with basically unlimited minutes.
To prevent bill shock: don't go over your allocated minutes and avoid roaming.
All the carriers want 1 or 2 yr contracts to sell you a new phone at a discount. You can avoid that and go month to month if you like, by either buying your phones used on ebay, or as I have for many years, find a local cell phone repair/trade-in guy, and buy a phone from him.