How much should I lie in my CV?

I wouldn't lie that much. You need to lavish yourself and do white lies on a resume. Not straight up "I worked at this place for several years" when you didn't.

I volunteered at an animal shelter for 3 months. I turned that into 6 months. I "helped the kitchen" when all I really did is prepare and place coffee for guests. I wouldn't lie about your last employment length because they'll check that. If it was a stupid project like my volunteering and it's not a reference with a phone number, I know they won't.

Also kind of off topic, but never ever joke during an interview. Light hearted is fine, but no jokes.

>>16953517
It's so easy to check this stuff out that I wouldn't even try to lie.

The best you could do is talk to your former supervisor, explain that a three-month sting looks bad and ask if he would agree to say you worked there six months. And that only works if they don't have an HR department to double check.

Lie as much as you like, its not like a person looking for a dishwasher or kitchen porter is ever going to get in touch with the CSI Miami to check you out.
In fact tell them you were head chef at Maison Eric on the Champs Elyseè in Paris, but gave it up due to stress, and you now prefer to work undercover for Michelin as they are thinking of starting up a star system for greasy joe diners. Tell them this info is confidential, but if they give you a job you will put in a good report to Michelin hq.