Here is my advice.
1) Make sure that you carry no debt before buying even 1 oz of Silver or Gold.
2) Make sure that before you buy that first oz, your family is well-fed, well-clothed, and has been to the dentist.
3) Before that first oz, make sure that you have ample (1 year minimum) liquid cash for emergencies.
4) When you decide you want to invest, make sure you set a budget and stick to it... feverishly.
5) After budgeting for "investments", don't put all your eggs in one basket. Spread it around to stocks, bonds, mutual funds and yes, your 401k, before PM's.
After you meet 1-5, then find a reputable and cost-effective vendor for your PM's. It may be via the big houses on the internet, it may be a small local mom & pop coin store or it might be from other "stackers" of PM's who don't just Buy & Horde, but also sell. Sometimes you can get the best deals from someone who wants to move a hundred oz of silver to buy a much-wanted gun with, or a couple of oz of gold for a daughter's first used car. They are out there...
When you start purchasing, you may get bitten by the PM Bug. Don't give in! If you budgeted for 4 oz a week or a month, or a year, stay strong.
If you need to "sell" because of an emergency, try selling on Classifieds like here on NES. You can sell for SPOT, which can get you a dollar/oz (or more) for silver than you would get selling on-line or locally. The buy is happy because they can save a buck or two at purchase. More for Gold. This develops networks and relationships. Both are as Good as Gold...
~Matt