There are many ways to find and evaluate bounty.
There are now many bounty management sites, or you can search in th

Well, there are plenty of types of bounties out there, for example if you consider the twitter account the ICO promoting the bounty has it's own rules about it, so you have to read their bounty thread in order to find the campaigns that fits you the best.

Will for me i choose a bounty that has good reward and short bounty. I also pick a bounty that has good historic manager and high rating in a ico rating sites

You must check the project background as well as the team, and you must also read the whitepaper that they provide, so that you can have a vision with there project.

                  

To bounty is an easy thing, first of all you should be an computer literate and know what is bounty. Now for you to choose bounty, you have to read about the bounty you want to choose and check or read the background read the whitepaper very  well and if what is written suits you, you can now register in any of the bounty either you register in signature, twitter or facebook etc, you must follow it up till the bounty endsi and you receive you token                  

You need to study the project documentation, their team and goals. Check manager. Check the site. Read more about bounty and how it is conducted.

It's not all about reading the white paper.
What are the things that you look out for in the white paper:
- You check to know the product or services they will be offering
- Whether the product has a competition and if it does; what are the chances of it thriving in the market i.e. any competitive advantage
- Analysis of the product has a verified and workable Github account, to know if it's a feasible project
- The Resume of the management and advisory team
- the social media duration, commitment and traffic to know how feasible that can be,
- How much was allocated for the bounty project and the expected duration before the pay offto know if it is worth the stress, etc

These and many more, after the analysis, will definitely give you a clue on which bounty to take part in

Aside The White Paper, you may look at the Past History with responses to its former ANN if it's a long existing Project that pays good. But if it is a new Project, I feel all rules and procedures must be scrutinized and strictly adhered to to earn requisite rewards

I don't believe that its whitepaper determine how profitable the bounty is. There are bounties that declared right from the start how much they are allocating. Some are less than $1M and you should pass that one. Only consider the ones that at least offer $2M.