Ideally don't have open monitors when recording in the room, but if you're close mic'ing the amp and put a bit of thought into where you position it in relation to the monitors then you can probably get away with it with negligible bleed that will just get lost in the mix.
I've heard of rare cases of people trying to get overcreative and tracking vocals in a control room with open monitors because they reckon the sound of the spill into the mic suits the mix, but I remain slightly sceptical of whether such situations exist where there is no other option to get the same effect other than to do this... if they really like it that much, why not get the vocals done cleanly then just record the sound of the mix being played through the monitors in the control room later on as a separate track?
Anyway, going off point a bit... really you would want to use headphones.
Even better is to shove the cab+mic in another room that is well isolated from your main room; then you can play and hear it through the monitors without having to worry about the spill from them, as well as the added benefit of being able to make better judgement and adjustments of the tone and how it fits in with the mix... when you record with headphones getting the right tone can be very hit and miss and require you to record a section, listen to it back, tweak and repeat, whereas with this you can properly hear how it will fit in with the mix.
If you keep the head in the room with you and run speaker cable then you can make some tone adjustments without having to move (though obviously mic placement is also as important as amp settings), plus its better to run long lengths of speaker cable than instrument cable.
As for cranking the volume, these really depends on the tone you're going for. For a rich distortion tone from a large valve amp then its often preferable to turn it up and find its 'sweet spot' which is likely to be at higher volumes... get those tubes glowing and some air moving
Some people prefer smaller tube amps for recording as they can get that tasty distortion at lower levels and with less fuss. You can also use a power attenuator like the THD Hot Plate so you can crank the amp but have the cab running at a lower volume, but these get quite pricey. In many other situations you can get a good tone a a comfortable low volume though.
the only thing is the volume , will i have to crank the volume up , and should i put something round the mic so it doesn't pick up the drums coming from my monitors 
