For those of you who are lazy

Get Illusion level 100



Get enough fortify illusion gear to make illusion spells free to cast



Get the Harmony master level Spell from the college of winterhold



Go to a populated area (Godmode_On reccomends riften) and wait for everyone to be outside



Spam Cast Harmony, depending on how many people are nearby you can max out illusion in 8-10 casts



Rinse and repeat until you are level 252

If you want to do this via console. The safest way to do this is using the advskill command. This command also levels you up as you normally would (the setav.skill) command does not level you up.You can make a batch file that will level up your skills automatically. Note that quests that are triggered via level-up will require you to level up again before the quest is triggered.Copy and paste the following into a .txt file, put the file in your skyrim directory and then in game open the console and type "bat filename" without the quotes. Reset your skills and repeat the process as many times as desired.;Combat SkillsAdvSkill Twohanded 1000000AdvSkill Onehanded 1000000AdvSkill Heavyarmor 1000000AdvSkill Block 1000000AdvSkill marksman 1000000AdvSkill Smithing 1000000;Stealth SkillsAdvSkill Sneak 1000000AdvSkill LightArmor 1000000AdvSkill Speechcraft 10000000AdvSkill Pickpocket 1000000AdvSkill lockpicking 1000000AdvSkill Alchemy 1000000;Magic SkillsAdvSkill Enchanting 1000000AdvSkill Destruction 1000000AdvSkill Conjuration 1000000AdvSkill Restoration 1000000AdvSkill Alteration 1000000AdvSkill illusion 1000000If you dont like using the console there are a few ways of doing this via exploits:You could talk to Ungrien in the black briar meadery over and over and level up speechcraft (VERY TEDIOUS)Edit: they fixed this bug you can no longer repeatedly talk to ungrien for free speechcraft XPOr(thank you Godmode_On for this little tip):Will add more methods as I find them (or as people inform me of them)