To drain the fuel you can either take off the fuel tank and just dump out the gas or pull the line off and turn the pitcock to the RES position and drain the gas out that way.
It wouldn't hurt to put some fresh fuel in and slosh it around and then drain that out.
The carburetor is more than likely gummed up as well. So you will need to take the float bowl off and clean it and the jets and passages inside.
Things you will probably need to do the job.
#2 phillips screwdriver to get the floatbowl off
Small flatblade screwdriver for the piolet jet
6mm socket for the mainjet
can of carburetor cleaner to spray out the passages
As far as what kind of premix and ratio to run you can ask 100 people and get 100 different opinions. I have had good luck with yamalube 2-R at 40:1. It works, runs well, burns clean and the bike has not died on it. Is it the best?