I have a Samsung Charge phone and the GPS almost never works properly. When trying to use Google navigation I get a "Searching for GPS" message and no navigation instructions.

Apparently this problem has been around for quite a while and has not been addressed. When I try the Samsung Galaxy 10.1 at the local BestBuy I get the same "searching for GPS" message. I was all set to buy an Android tablet, but now I'm thinking about getting an iPad as I plan to use it when travelling and plan to use the gps.
Two factors are involved in a phone or tablet of any make or model (including iPads) locking on to GPS signals and how fast the lock occurs:
1 - The GPS device needs to lock onto several satellite signals at once in order to get a lock, then download the location data including time and sync info which is part of the GPS signal. This takes several minutes if there is no Assisted-GPS info available (like cellular).
2 - The device needs map info which requires some kind of data connection, either WiFi or 2G/3G/4G cellular. Without that data, the apps can not download mapping info as the devices do not store complete maps on the device, just cache some map tiles for local mapping. So even if it gets a GPS lock, it won't display mapping info without a data connection.
Of course, this is using ONLY the GPS sensor in the device. As Szadzik said, having WiFi or cellular network data turned on will increase initial lock speed into several seconds instead of minutes outdoors. This is due to the Assisted-GPS chips in most current devices. The A-GPS device will look for cellular network data and get a rough location within a few kilometers which is accurate enough for weather app details or get a rough lock on your location. The GPS continues to look for and lock onto several satellites for a fine location lock which may take another 30+ seconds outdoors. Indoors the lock can take longer, but as long as several satellite signals are available, the device can lock indoors in houses. In apartment buildings or large stores, the concrete and steel structure overhead often prevents enough signal penetration to provide a GPS lock.
I have an app for geocaching that shows my exact location in coordinates and it doesn't need a data connection as it can store geocaching data in a GPX file that I can download to my devices. My Galaxy Tab 10.1 3G will get a rough lock in my house in about 5-10 seconds and the app shows accuracy is about 2200 meters (2.2 kms), along with a fine lock in about 30 seconds with accuracy of 5 meters. This is because I have cellular data available. But if I turn off the 3G connection (airplane mode for example) without WiFi, a GPS lock can take 3-5 minutes but once achieved, that lock is accurate to 5 meters.
I also have a Samsung Nexus S and use the same app on it. Results are similar on the phone. My wife has an HTC Desire and again we get similar results. My daughter has an HTC Legend and it's about 30% slower getting a lock, but it does it too.
I have a Garmin GPSMAP 62s for geocaching which is a dedicated GPS device (shock and water proof and runs all day on one set of rechargeable AA batteries). It locks in seconds and is more accurate and can get a lock inside buildings, under heavy foliage, etc. But that's all it does, no voice or data on it, just GPS location info. But it gets that GPS lock in places where the phones or tablet can't even get a single satellite signal or make a phone call.
