For what purpose you wanna buy laptop? Is it just household purpose (email, online videos, music, movies etc) or something enterprise level of use (e.g. developer's tool, utilities?). 

If it is for household use, get something upto 2GB RAM, 160GB+ Hard Disk, 1.7GHz+ Intel Processor..

For enterprise use, go for higher RAM at least 4GB RAM, and higher speed. 

Few facts you should know-

1. No matter what brand you buy, average lifetime of a laptop is 2 years. Some hardware issue appears after that period (Ironically, your warranty expires by that period). so RULE 1- LAPTOP'S LIFE IS 2 YRS whatever you buy..

2. Don't go for too big hard disk size. No matter what  is the size of storage, it is always less - one day, it will be full. Larger hard drives create issues, and they add extra weight.. Something around 200GB would be perfect. so RULE 2 -  NO BIIGGG HARD DRIVES.

3. Hight graphics ? Video Games? Desktop virtualization? Go for higher RAM. Rather go for Mac.. otherwise, DELL is fine.They have better / robust peripherals.

4. Don't spend more that 700 bucks in a laptop.

5. Don't shut down (turn off) laptop too often. Internally, it does lots of flushing/restoring work during shutdown/startup process. Rather just close the lid and it goes into hybernation.. Thats good. You should shutdown/restart once in a while for updates or after scanning.