If you know what your at its easy.. very easy.. get yourself some cone spanners and just give it a bash.. you don't need fancy cone spanners from Park or the likes... this cheap and cheerful set from Cyclo will do the job nicely..
http://www.chainreactioncycles.com/M...?ModelID=32405
First thing I'd do is try identify which side is loose... but normally, when making simple adjustments to the cones you should only adjust the non drive side...
But... if you know or suspect the cones on the drive side are loose then its a bit more hassle as you will need to completely remove the axle from the hub to re-tighten the cone & lock nut on that side.. be prepared for bearings to fall out all over the place while you do this..
Take this opportunity to clean & inspect the old bearings for damage before re-fitting them.. if you've gone this far replacing the old bearings is a good healthy step to take.. if you don't have new bearings then check for surface pitting on the bearings, cone and the hub body.. worn bearings and cones can be replaced but if the hub body is worn or shows signs of pitting then basically the hub is fooked.. putting in new bearings and cones won't make the slightest difference.. the hub can still be used no problem but you will never get the bearings running smoothly again..
If you do take out the axle and it is the drive side cones that were loose.. then tighten them in the
original position without moving them.. if you need to remove the drive-side cones for any reason then measure the distance from the end of the axle first... if you don't put them back in their original position you will end up making a pig's ear of the rear spacing
(rear wheel will sit off centre in the frame and your disc rotor won't line up with the brake caliper) and give yourself a whole lot of work to do to set them back to the correct position..
For adjusting cones (non drive side) without removing the axle... just make small adjustments (as in 1/8 to 1/4 turns) and check for tightness each time you make an adjustment.. there is pre-load to consider from the lock nut as well, so even when you think you've got the correct setting at the cone, once you tighten the the lock nut it may start to feel tight again..
Check out some of these guides for Shimano hub service... The procedure is pretty much the same for all Shimano hubs.. there is very little difference from year to year.. model to model..
http://www.parktool.com/blog/repair-...and-adjustment
http://www.mountainbikerides.co.uk/f...b-service.html
http://steveukmtb.wordpress.com/shim...-cup-and-cone/
http://www.cyclistno1.co.uk/features...ub-service.htm