That said, there's something in the Blue Card arrangement that allows one to come here for up to six months as a "job seeker". I believe that when doing that you need "only" provide evidence of self-support, a place to live, and insurance, that latter IIRC need not be conforming to German standards. Also IIRC this visa is non-renewable.
1. Proof of Health Insurance. 2. Rental Contract 3. As many contracts or letters of interest from businesses as possible. Particularly if these are in English, they don't scrutinize them too much. If you simply have an open engagement letter for some hourly rate, perhaps an estimated (but not guaranteed) number of hours, they will look kindly on this, even if it doesn't actually obligate the other party to ever pay you anything. 4. Business Plan. I would generally shade this on the low side. You will look better on your renewal if you exceed your projections. It does need to be at the very least about 18k EUR/yr. 5. Historical income, particularly from self-employment 6. Bank statements, any evidence of assets you can dig up. Print these out for a couple of years. 7. Any degrees and transcripts you have 8. Personal references. 9. Any professional awards, etc 10. If you're married, an official marriage certificate.
The main strategy here is to overwhelm them with paper. They love paper, particularly if it has some sort of official looking stamp on it. If you show up with 100-200 pages of documentation, you should be virtually guaranteed to get the visa.
If you are worried or want to increase your chances, hire a lawyer and have them show up with you. The immigration people seem to see you showing up with a lawyer as evidence of seriousness and professionalism.
I can say that I showed up with my wife, and unfortunately she didn't have any job offers when the appointment rolled around. Between our copious documentation and a lawyer present, they issued her visa without the (required) job offer.
Turns out, we are already very good at attracting immigrants with an education and earning power above the national average, and every book and form you throw at immigrants only discourages the "wanted" immigrants. I also object to the discrimination between "wanted" and "unwanted" immigrants but that is another topic...
The problem with the theories about undercutting wages of "native talent" is that there is virtually no unemployed native talent.
Of course, all Germans believe they are paid too little. The only way wages would rise dramatically would be if employers went into a crazy competition mode, and they seem to know that this would be bad for every employer. Higher wages only serve to "steal" employees from another employer, they don't increase the work force per se.
There is no comprehensive way to tell if immigration lowers salaries, since you can't just add and subtract jobs in the complex system of a national economy. Also, I find it hard to justify any right for "native talent" to shut out "non-native talent". Both are human beings and there is no such thing as a birth-right to higher compensation.
The incentives are exactly the opposite of what made Germany big in high-tech manufacturing. We treat developers as the mediocre, cheap code monkeys they often are (using the word "mediocre" so I don't have to swear on HN).
Developer productivity and project management is a large field. I sometimes feel that programmers, especially the idealistic ones, tend to overestimate their own performance, and underestimate the problems of project management.
The way to measure developer performance is easy though: you have to look back instead of forward, then you see what people get (or rather: got) done.
Sure, if you're an idealist and aren't used to estimation, you tend to underestimate the effort for a given feature or bug.
I see the rigid stratification of German education is still in force.
The U.S is the pathological case when it comes to visas.