Azerbaijan is known for complex visa regime with the new visa rules popping up all the time. Situation can confuse tourists even further as as different AZ embassies interpret the current visa rules in a different way and it is highly recommended to check the rules and requirments directly with the embassy where you plan to apply.
Roughly speaking there are 2 ways that one can obtain Azeri visa: electronic visa (e-visa) or traditional sticker visa that you need to apply for through the embassy.
1. Evisa should generally be your choice as it is cheaper, less time consuming and allows you to keep your passport with you all the time. The main disadvantages are unpredictable processing time (from 15 to 30 days or even more), requirement to submit hotel booking confirmation for the whole or part of your stay in Azerbaijan. You can't apply for evisa directly to Ministry of Foreign Affairs, you need to get support of one of authorised Azeri travel agencies that will apply on your behalf. Many people get trapped with http://evisa.mfa.gov.az/ service, apply and wait for weeks in vain, without even realising that this service is not for individual tourists. The whole process is done via emails, you send required docs to travel agent's email, they submit them to MFA and when evisa is ready forward it to your email address as PDF attachement that you just need to print out.
2. Traditional visa is obtained by applying through the embassy. Most likely you will need to have a Letter of Invitation to be able to apply. Though the problem here that every single AZ embassy have their own requirements and the process differs from embassy to embassy. It is usually much quicker but might be more expensive (mainly for US and UK nationals) and also involves either posting your docs or personal visits to the embassy.
We have complied an embassy report and try to update it regularly on what are the latest requirements for visa. Still we can't vouch that posted requirements are valid as of today so it is always advisable to check directly with the embassy on current situation. Check the page here for the latest developments and various ways of how to obtain your entry visa to Azerbaijan.
Also, check information and requirements on registration in Azerbaijan and how you can make it. You will need to register within 10 days since your entry.
Please do not hesitate to contact us for piece of advice, but do mention in your enquiries your nationality, planned travel dates and the place of application so that we could suggest you the best possible soluiton.