Laptop hard drives are fairly generic. There are 2 major things to check for:
- Interface type.
- Drive height.
For interfaces, SATA is the current standard, with IDE (also seen as PATA sometimes) being an older standard. laptop IDE drives are still being sold, so make sure that you're not buying one of those, since your laptop uses SATA hard drives. IDE drives are not very common anymore though.
Regarding drive height, most laptops are designed to accept 9.5mm high drives, and most laptop drives are built to this height. There is a lesser used standard for 12.5mm hard drives which is less common. AFAIK, only a few 12.5mm drives are readily available, mostly the extremely high capacity 750 GB and 1 TB laptop drives.
Beyond that, it's all about features and performance.