Direct approach is the best option. If a consultancy calls and informs of a technical job for Electrical/mechanical fresher, it could possibly mean this same company. But they will demand a registration fee and half the salary package for the first month as service charge.
Interview is held at the office by most probably the project manager/team leader in charge of your department. Technical questions can be expected. Event though they do not require any of those knowledge to work in the company, it is simply a filtering criterion defined by the interviewer himself. Communication skills are necessary as that is the sole purpose of the interview. Sow them that you are confidant and ready to face any pressure situation. Another trend that the company shows is hiring of engineers who are graduated from reputed universities.
Being a mechanical engineer, I faced questions from Materiel Science (Definition of hardness, toughness etc. ) from Manufacturing Process (Annealing Quenching etc.)
Once you are hired you will possibly get the confirmation on the same day.