If the laptop already has an OS, make sure to back up your important files first.
Also, if you have partitioning software, try to partition the laptop's hard drive, leave the already installed OS alone, and install Solaris in its own partition.
Definitely check out the site Sunny's mentioned. It's got some great information.
My biggest problems with Solaris for X86 have been video card related. You might be able to get the OS to install with a generic video driver, but you need a better match if you plan to use CDE or another Solaris GUI desktop.