Before buying laptop/notebook RAM/Memory, always check for compatibility to see what your laptop requires.  A great place to check for compatibility is at crucial.com.  Just enter your laptop model and it will tell you what specifications you need to look for and what your limit is. 

Installation:

1. Before installing RAM, always shutdown your laptop and unplug its AC adapter and remove its battery.
2. Find access to the RAM slots, some have an easy accessible slot under the laptop which you can use a screwdriver to remove the cover.  Some laptops are a bit more tricky when the slots are under the keyboard and are not easily accessible.  Take note that it would require some work to take apart the laptop and might even void warranty.
3. Laptop RAM are sitted in the slots by two arms, one of each side. Simply push the arms outward the RAM stick will lodge of out place.  Now you can pull the stick out of the slot.
4. Installing the stick is also easy, all it requires is to push the stick into the slot at an angle, then push down towards the arms.  The arms will lock the stick into place.  Make sure the RAM sticks are both seated correctly before starting the computer.

Testing the RAM:

1. Always test the RAM to ensure it is not defective.  A great program out there that tests RAM is called Memtest86.  Google the program and download it.  Once downloaded burn the program onto a disc (the program extension you should download should be an .iso format so you can use Nero to burn the image).
2. Make sure your laptop's boot priority has the cd-rom optical drive as the first boot option.  You can enable this option through your system's BIOS that you can usually access within the first couple seconds of power-up.  Some laptops require you to press the DEL button, or F2, F10 etc.
3. Make sure the Memtest CD is inserted into the laptop when powering it up so it can boot off the CD.
4. Memtest will then test the RAM for errors by sending it different packets to ensure it is receiving the sending data correctly.
5. I highly recommend to run this program for atleast 12 hours to make sure the RAM are fully functional.  If you do not have this amount of time, let it go through atleast 5 passes.
6. Once you have fully tested the RAM using memtest, log on to your operating system and run a few programs to make sure your operating system does not have any problems with the RAM.  If the RAM passes all tests, you have successfully installed your piece of RAM.

Take Note:

• Some laptops are very picky so when looking for RAM, try sticking with brand names.
• Some RAM are actually downward compatible, for example a PC2700 (DDR333) RAM can run PC2100 (DDR266) mode when the laptop only runs PC2100 RAM.
• There are two current models of RAM in the market now, DDR and DDR2.  Both are not compatible with each other since DDR laptop RAM are SODIMM 200-pin sticks whereas DDR is 200-pin but different pin setup. You will know instantly if you have the wrong stick since they will not fit on the other slot.
• When using two sticks of memory, try to have them the same brand and same speed so you don't have any compatibility issues since some RAM are picky and require the same RAM to properly run.
• When upgrading your RAM to a higher speed if your laptop supports it, you will need both sticks to be the same speed, for example you laptop supports PC3200 DDR400 RAM but a single PC2700 RAM is installed, you will need both sticks to be PC3200 to be at DDR400 speed.  If you install a PC3200 and PC2700 RAM sticks together, the PC3200 will throttle down to PC2700 speed.
• Some laptops have size limits. For example a laptop's RAM limit may be 1GB/1024MBs, so even though you can physically put 2x 1GB RAM in the laptop, that laptop will only recognize 1GB of it.

Some RAM sizes and specifications:

DDR

• PC2100 DDR 266, runs at 266MHz.  Usually is required for laptops with a CPU Processor with a 266MHz FSB like AMD XP m CPUs.
• PC2700 DDR 333, runs at 333MHz.  Usually is required for laptops with a CPU Processor with a 333MHz FSB like AMD m64 CPUs and AMD Sempron.
• PC3200 DDR 400, runs at 400MHz.  Usually is required for laptops with a CPU Processor with a 400MHz FSB like AMD m64 CPUs and Apple.

DDR2

• PC3200 DDR2 400, Runs at 400MHZ.  Usually is required for laptops with a CPU Processor with a 400MHz but usually the norm for DD2 laptops will take DDR2 533 RAM.
• PC4200/PC4300 DDR2 533, runs at 533MHz.  Usually is required for laptops with a CPU Processor with a 533MHz FSB like Intel Pentium M Centrino and Celeron M CPUs and also AMD Turion CPUs.
• PC5300 DDR 667, runs at 667MHz.  Usually is required for laptops with a CPU Processor with a 667MHz FSB like Intel Core Duo CPUs.