I recommend something with a Solid State Drive (SSD) and a full HD (1920x1080) screen, and 8GB or more of RAM. The SSD is a big factor, in allowing you to launch programs, start up, and reboot quickly. Also, since it has no moving parts, it is not as susceptible to damage as you are moving it around, if it gets dropped, impacted, etc. On laptops nowadays, I recommend a 1080 screen. 768 pixels in height is just not enough for modern day workflows. 1080 will allow you to see more lines of code at a time, and to get more on the screen. I recommend 8GB of RAM or more so you don't ever approach dipping into virtual memory space, which is much slower. By the time you load the OS, a browser or two, and some programs, it's easy to max out 4GB these days.
If you were really on a budget, you might consider
this laptop. It's essentially the lowest priced laptop with a 1080 screen on the market currently. While it lacks 8GB of RAM and an SSD, those things can be added with a bit of work involved, however it does take someone technologically inclined to do it.
As a disclaimer, I have no direct experience with this particular laptop.
The good news is, you're in the right time of year for buying laptops. This is right when all the deals are to be found.