I agree with a couple of the others - I don't see the value in finding hot spots that the laptop cannot see. I agree that, if you knew they were there and what direction the signal was coming from you might be able to move closer. It just seems questionable.
Sandra, to take a high level approach to your question about "how do I secure it?" Here are some ideas.
If you own the hotspot (have a wireless router hooked to an internet connection):
1. Turn off polling
2. Turn on WEP - this means the every computer trying to access your router has to have a key. A 128bit key is better, a 64bit key is better than nothing. This encrypts the signals between the laptops and the router.
3. Turn on MAC address filtering - every network card has "serial number". Some routers let you only allow the serial numbers/MAC addresses in a list to use your connection. This keeps others from using your connection to do bad things.
For the laptop security:
1. Don't EVER connect to wireless networks where you don't know the source. There are too many traps out there. It might appear safe but....
2. Install a personal firewall. I personally like Zone Alarm and they have a free version (www.zonelabs.com
3. Install antivirus protection. I personally like AVG and they a free version.
4. Install spyware protection. I personally like Spybot Search and Destroy and their software is free but do make a donation as they request.
I view wireless security in the same vain as the two bear hunters. One hunter shoots the bear and it doesn't die but starts chasing them. As they run away, one asks the other, "how are we going to outrun this bear?" The other replies "I just have to outrun you." Security can be broken by professionals with the right knowledge and equipment. I just want to keep out the amateur hackers and make my situation more difficult to deal with than my neighbor's. Most often, those with bad intentions will select the easiest targets.