As a RDP client, there isn't much you need. What RDP does is essentially send keyboard and mouse input, and provide you with the screen output over a network/internet connection.
A larger screen, capable wireless card (and internet connection), preferably a large/full size (with numpad) keyboard and a good touchpad (or wireless mouse) would help. Generally, graphics is not an issue, you are not going to be playing any games or even watching videos over RDP. To prevent resizing of the desktop and windows, it helps if your laptop screen is the same resolution as the server computer. From personal experience, a very small screen, such as on a netbook, would be no good. A not-so-standard resolution (1366x768 on my laptop) has some issues with fullscreen.
Multi monitor support gets more complicated, on the software (operating system) side. The server computers have to be at least Windows Vista for basic (span) support, and Windows 7 Enterprise/Ultimate / Server 2008 for full (multimon) support. The client needs to be at least v6.0 (included with Vista) for span and at least v6.1 (included with Server 2008, Windows 7 has v7.0) for multimon. More information is available on this MSDN blog. Also, this guide has some detail how the Windows version effects multimon support:
If you are trying to use a dual-monitor computer running Windows 7 Pro to remote connect into a remote dual-monitor PC running Windows 7, the remote machine must be running either Windows 7 Ultimate or Enterprise. Verified this just this weekend. The user went from XP to 7 Pro, and the loss of dual monitor during remote sessions was disappointing. They upgraded to ultimate, and dual monitor use during remote sessions was restored. Microsoft needs to do a much better job of this requirement in their product materials.
This page has a table of support, but the v7.0 row does not look quite right. It also provides download links to the newer clients for older operating systems (e.g. v7.0 client for XP).
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I've gathered that graphics card is not particularly important (http://superuser.com/questions/199052/is-a-good-graphics-card-important-for-remote-desktop) as most rendering will be performed on the server I'm connected to.
– Blue – 2012-04-05T06:06:56.000