There is one thing I check before getting involved in a bounty... Their history and their rating,I only go for highly rated projects that didnt just materialize from thin air,and I never go for bounties that has an invincible team,the team has to be fully visible.

Some big projects have to much participators.. Then the money is split to all participator.
Sometimes a smaller bounty can make more.

I give you small tips:
Check team/founders.
Check rank of bounty manager
Check existance of MVP/DEMO product
Check how possible is to implement all company wants.
Check is their product will be really useful .

Determining the right campaign and not, to get some bitcoin or other altcoin. We must know the manager and the company website to be advertised. We should search on google about whether there is or not. If there is a sense that the company is indeed there, and if searching on google there is no company name in question should be suspicious. That's all my opinion that I used to do until now.

Yeah, you are absolutely correct to read whitepapers before indulging yourself (and your precious time) in bounties. You may also want to look at the profile of the devs involved in the project, most developers work for different tokens and they can be easily identified by you if you would carefully read and do your research in forums like this. One more thing to consider is the wallet (hard wallet, ledger, etc.); if the bounty likes you to get wallets from suspicious sources then you must think twice before extracting one - trusted wares are uploaded in trusted sites. But anyway, at the end of the day, bounties are bounties... all of those are worth a try.

Choosing is simple and easy but yet if you dont check properly there are some campaign thats not good to invest specialy those campaign that there some project that almost the same feature and thats the reason why they are unsuccessfull project.

You must check first the project. You need to study the white paper and the development team. Then check the bounty pool and the budget for each campaign.

Actually we should look at the project as well. Usually mining project is good because actually we need more minner. I got a lot of money by participating in small project but good. Now I stilll hold that altcoin, thanks to God because make me joined that bounty.

Well, I usually check the team more than the bounty because it's not about how much you will receive but on how big the project will achieve.
Just like Populous for example, the bounty is not really that big but the price rise x50 before it fall I guess, so bounty hunters who gold benefit a lot of the success of the project.