Here is the website where you could get all the visa information if applying in India:
And regarding to your question, What documents should I submit to prove that my return is guaranteed?
Although requirements are more or less the same for all Schengen countries, it is written in all Schengen visa application that compliance with required documents doesn't necessarily means a visa would be issued.
Following are essential in order to qualify as a successful candidate:
Proof of employment:
If employed, letter from company stating monthly wages, continuing employment after period of leave and duration of
If self employed/ business owner : company registration with relevant
authorities at your home country, tax registration along with last 2
to 3 years tax returns, company bank statements along with maintenance
Proof of sufficient funds for duration of stay, (Bank statement of the past six months to 1 year)
proof of propert (under applicant name if required by embassy).
Proof of Any other document to support his/her application.
proof of rental income(if applicant receiving monthly decent income
,just to strengthen the visa application)
The website also requires applicants to note few updates; however I just emphasize the following 2 points because those are relevant to your application and question.
Salary slip recent 6 months
Leave sanction letter on company letter head
As it is already mentioned in VFS website, the application most likely would not be accepted
however applying for a Schengen visa without employment could strongly result with the following two refusal reasons:
1. Justification for the purpose and conditions of the intended stay was not provided:
•The relevant documents (please see visa requirements) were not submitted
2.Your intention to leave the territory of the member states before the expiry of the visa could not be ascertained
•The professional binding (existence of a fixed employment relationship)
•The employment relationship has not been established