Everything that pawpaw said!
I like to try and keep things moving too. so ever 2 weeks/month - give the wheels a good spin, pump the suspension, if you cant start the engine then cycle it round on the kicker a few times. Pump the brakes and push the pistons back in a bit by pushing the calipers and sliding them on the carrier pins.
I had my brothers RM125 stored for over 8 months, did everything posted above and it started up 3rd kick and didn't take much prep to get it ride ready. I prefer to drain the fuel and start fresh personally, but if you don't you're better off having the tank full to reduce the air gap. it will help keep the fuel better for longer.
A good coating of oil on the chain and a general spray of WD40/GT85 is a good idea if it gets damp/cold where its stored.