The best way to look at internet security is to think of an Onion. The more layers the better. For home you need at least 2 layers but for business you need to look at more than 2.

At home you need to protect your internet connection and also as further protection you need to protect the computer. So the 2 layers are router and anti virus.

So here are some do鎶?and don鎶皊 for your home network

Do always change the default admin password on your router / modem
Don鎶?open ports on the router
Don鎶?allow wireless unless you have a very secure pass phrase
Do use WPA gardenscapes hack online / PSK security for wireless access (WEP can be 鎻穜acked?within 5 minutes with the technology available from the internet.)
Do use a anti Virus / anti spyware solution ?Even a free one is better than nothing. As a free one Microsoft Security Essentials is good but you get what you pay for. At a commercial level we have found that Kasperski is a very good product
Don鎶?install P2P torrent applications on computers unless you know what you are doing.
For a business there are a few more considerations that have to be taken into account. For a business you need to implement 3 layers ?router ( see below), centrally managed Anti Virus, intrusion detection and management reporting.

So here are a few do鎶?and don鎶皊 for your business security, in addition to the ones above:

Don鎶?purchase an off the shelf residential router and if you already have one, change it out as soon as you can afford it. The Cisco ASA 5505, Fordigate 50C are good examples of better protection for your business and they are around $1000.00
Do use a centrally managed anti virus application that reports back to a person via email.
Do use a router that has sophisticated intrusion detection and can track both external access and internal use.
Do use a router that has more details an anti Spam component
Do use a router that allows your business to protect your users from themselves ?accessing inappropriate internet content for instance.
Do use a router that will protect your business from compromised web sites
Don鎶?allow your users to download and install P2P applications on any of your office / business computers.
The internet can be a very nasty place, yes it is fun, informative and educational love here but you need to be in a position to protect yourself and your business. Just imagine your business reputation if your business was compromised by a internet hack.