In my case, alam kong burned out na ako pag:

1.) Not even a droplet of a creative idea or solution pops in my head
2.) Kagigising ko pa lang, lethargic na ako
3.) Can't sleep well at night.
4.) Madali akong nagsasawa kahit anong ginagawa ko.

How to cope? Simple lang akin - I take a leave of absence or do something that has absolutely no relation to the project/work that I was doing when I crashed and burned. However, each of us is a different person so IMO we all have different burn-out symptoms and ways of avoiding it.

How to avoid? In my line of work, malabo kase if I avoid, I'd be out of the job.