There is a ton of info out there about this. One of the better sites is http://goldsilver.com/ run by my pal Mike Maloney. His prices are a little higher but his presentation is nice and he offers a great deal of info. He also has lots of YouTubes.
The nexus of the decision revolves around "premium over spot". Junk silver coins typically sell at the lowest premium over spot and offer:
1: recognizability 2: divisibility. 3: difficulty of counterfeiting. I would avoid 1: silver dollars and 2: 40% silver eg; Kennedy halves from 1965-1969. Although I am always happy to blow a few hundred bucks on small, well-priced batches of either, that is only because I have tens of kilos of either, bot long ago at well under Ag $20. Silver dollars have been widely counterfeited and carry a substantial premium over spot, so it's best to avoid them for the inexperienced buyer. Still, a few of these don't hurt. Common dates in remarkably good condition, 100+ years old are very nice things to own and hold in your hand.
The next step up is generic silver rounds (should not be called "coins") which can be had, on sale, for buck over spot...sometimes as low as 69 cents over spot.
The next step up is US Silver Eagles which are $2.50-$3 over spot. Gorgeous coins, whether or not you/they decide on SEs as the primarily vehicle/form, IMO every silver bug ought to own some Eagles and/or Cana Maple Leafs. Although Eagles are priced this much over spot---that premium will come back to you if and when you/they decide to sell.
The easiest way to buy junk silver is to buy a bag or a half-bag of $1000 face value, and those bags are traded, sealed, just as they are. Downside: A bag of junk silver is a 55 lb bowling ball sized bundle. A bag comprised of all half dollars sells at a slight premium over quarters or dimes because halves are almost always less worn than circulated D's and Q's and thus a given qty of halves will weigh slightly more than the equivalent face value of smaller denoms.
IMHO, the SAFEST way to buy silver of whatever form is to dollar-cost-average into a batch of your favorite form, some every month.
A more fun way is to go to coin shows http://www.coinshows.com where these coins are widely sold.
Most states have a minimum bullion purchase (in CA it is $1500) to avoid sales tax, and obviously that is desirable.
Most people who like and wish to own silver stop or slow down buying junk silver at a certain point and go for .999 rounds/bars/Eagles.
Many dealers offer free shipping (Merit Financial) on the first order over $2500.
APMEX is a popular site and excellent source; not the best prices but easy to look up prices on virtually any form you can name. What I like about APMEX is 2 things:
1: you can, once you sign up, buy silver overnight on a price dump, should you wish to do so.
2: Order, which means you lock in a price. Then send them a personal check. The check will take 10 days or so to clear, but this way you avoid wire transfer fees.
I have bot from them and sold to them many times. They are high on shipping, usually $25 minimum.
Tulving tulving.com usually has the best prices but steep minimums and often delayed shipping in high-demand periods.
There are several dozen other sites who can supply coins...the differences are very small.
Some that come to mind that I have used myself:
http://www.golddealer.com (aka CNI)
http://www.gainsevillecoins.com <<<watch these guys for great sales on rounds.
MeritFinancial.com (free ship on first order)
dozens and dozens more. 99% of these very, very reliable. No slight is intended on any I have not mentioned.
Best of luck!