Well so far much has been said already.
As you will not really be a heavy gamer, you do not need a "dedicated"-graphics card. Also about whole virus stuff, well i myself am a Linux user and i also have no problems with it. Not a big fan of Mac's as much is restricted. Do remember a Mac-book doesn't work the same as Windows, so you need to adjust a bit to it if you never have worked with it.
Now a days a SSD (type of harddrive) is STRONGLY recommended if you ask me. A SSD type of harddrive is MUCH faster in other words booting up and working on your laptop goes a lot faster. So to translate it in to geek language
Size: around 15 inch is kind of oke. That is not to big but also not to small.
CPU (Processor): A Intel i5 processor is fast enough but not overkill. So that would work well for you. Right now i believe the 6th generation is only available for laptops. The higher the generation the lower the power consumption is and often also faster.
Memory(RAM): Now a days 8 GB would do the job as i assume you do not buy it to last 2 days, but a couple of years at least.
GPU (Graphic card): As i already said no dedicated graphics card is needed. So no AMD or Nvidia graphics card. The built in Intel graphics card is sufficient for the things you want it to do, as it also saves much battery.
Hard-drive: I earlier said a SSD type if it is possible. However they are more expensive and 250 GB at max is enough for you. 120 GB if you ask me you will encounter more problems in the future.
Battery: Now a days many have 4 cell. It is oke, but IF possible 6 would be more of a good deal. This lasts i believe maybe till 6 hours or longer, but again majority of the laptops have 4 cell and that does the job.
Keyboard: Now a days many keyboards have the keys a bit separated from each other to prevent dust getting in to it. Do also be ware of that. As the ones that do not have this, is rather annoying. Also, do you want a dedicated numpad area? Like a old-school keyboard? It is handy if you work or will work with numbers.
Card reader: Many times we also have to deal with sd-cards and a sd-card reader also becomes handy. So also keep that in mind.
Brand laptop: Well what do you want as the OS (Operating System)? Do you want Mac-Os? Do you want Windows? Also with this keep in mind that on Windows more software is available than on Mac-OS. Laptops with Windows you can choose between many different kind of laptops, while Mac you are rather limited. The brands that i DO NOT advice..are Acer, Packard Bell and also Asus. I have a Lenovo and till now does it job very well.
Extra: Remember to have a decent amount of USB (USB 3.0 at least being 1). Also think about VGA or HDMI output to connect it with a projector for presentations. If it only supports HDMI, you can buy a converter (HDMI-->VGA). A DVD-rom/Blue ray is not necessary.
Will you also be using it often for Skype kind of applications? (Camera, good dual microphone for suppressing background noise).
These are a bit the basic things you should keep in mind. Also if you have found some laptops that you maybe want to buy, i would advice you to post at max 3 laptops so we can help you further more with the pros and cons of them.
Keep us updated

. Happy hunting.