I'm considering using Indiegogo to raise money for my project. I've been self-financing up until now, but it slow going. So the hope is to raise funds to bring in outside help. This leaves me with a decision regarding what to offer as an incentive to potential sponsors. One of the ideas is to offer advance copies of the game or a special edition version. This raises the question of how this work.

The game is almost far enough along to submit to Steam to get green lit (just not there yet). But at some point it will get Steam approval. This means I will need to get a bunch of keys to send to contributors. How does that work? The keys will also need some sort of identifier to tell the game that 'this person is contributor, so turn on the incentives'.

One other question -- I'm doing the development using the UE4 engine. Epic has a test Steam cloud Id to tinker with, but it's rather limited and crippled. Can you get a game ID from Steam ahead of being green lit so that the full cloud interface can be developed and tested?

I'd be interested in hearing about anyone's experience using Indiegogo and what pitfalls they ran into. Suggestions for incentives are also welcome.

How does that work? The keys will also need some sort of identifier to tell the game that 'this person is contributor, so turn on the incentives'.

Steam allows you to generate keys for your game. You use their tool generate keys and hand them out. If you want to have special keys for contributes you just add the content as dlc and have keys given out for the dlc.

Getting greenlit is the beginning of your partnership with steam. It's the point where you sign all the contracts for them being your publisher, so that's when they give you access to their systems. You should aim to get greenlit a LONG time before you plan to launch.

As above you can make DLC and different versions of your game, and generate as many keys for them as you like. The only downside is that as of recently, any reviews from people who got the game via a generated key don't count towards your games average review score, and they get tagged with "got the game for free", which often just isn't true... :(

Getting greenlight is the beginning of your partnership with steam.

This will be changing pretty soon as steam has announced they are getting rid of greenlight. So any developers will be able to release their games on steam for a undetermined fee atm.

and they get tagged with "got the game for free", which often just isn't true... :(

This happens with any steam keys acquired outside of the steam store. Which as Hodgman pointed out isn't always the case that it was free. This will happen if you sell steam keys from your own web store.