For three you need to use the Mini-displayport. The other two are up to you and from my experience it really doesn't matter which ones. I have mine setup to the two DVI's and one on the DP but I have also used the HDMI and it made no picture difference. Again you do have to use the mini DP for your third connection.
Cable wise just get some shielded DVI cables and a DP cable and all will be well. I suggest your monitors be able to accept DP as a lot do not. If you do not get DP capable monitors then you have to use an active adapter to change the DP to DVI or HDMI if you want to EyeInfinity.