The right date and time, chosen against your chart
A muhurat from a printed almanac is chosen for everybody. A muhurat chosen for you is checked against your own chart — your dasha, your Moon, and the specific thing you are about to start.
Gautam works from the panchang for the window you give him, filters for the tithi, nakshatra, yoga and karana appropriate to the event, removes what falls in Rahu Kaal and the inauspicious periods, and then checks the shortlist against the charts of the people actually involved. You get dates that work rather than a date that is technically auspicious for the population at large.
When this is not the right choice If your window is less than about a week, say so before booking — there may not be a genuinely good muhurat in it, and Gautam would rather tell you that upfront than sell you the least bad option.
As early as you can. A wider window gives better options, and for weddings the venue is usually booked before the muhurat is chosen, which is the wrong way round.
Yes — he will find the best time within the day you have. It is more constrained, and he will tell you honestly if the day itself is a poor choice.
Yes. Muhurat depends on local sunrise, so a time band correct for Mumbai is not correct for Delhi. Always give the city where the event happens.
The main ceremony has its own muhurat. If the registry, the griha pravesh and the reception all need separate timings, mention it when booking so the fee is clear before you start.
Not sure this is the right one? Ask first — you will get an honest answer, and no charge for asking.