We always recommend couples to choose their venue first then choose the rest of their wedding professionals as soon as possible afterwards. Saying that, getting a decent (doesn't have to be number of guests before choosing a venue is vital. We have had situations where the venue has run out of space to cater for guests on the day and also had situations where the venue has been too large for a small number of guest.
With regards to vendors, in our opinion and experience we can say that venue plays a significant part in coming up with the final cost for almost all (however not all). The venue size, layout, location and acoustics influence the final cost.
For example a DJ needs to know venue size and acoustics to get the correct sound system and lightings.
A Decorator needs to know the hall layout, logistics in terms of ground level, stage size and guest numbers etc to offer you the final cost.
A Bridal car will need to know pick up and drop off address before making a booking with exact costs.
Photographer/Videographer may need to know lighting requirements, number of cameras or travel times between shoot locations etc.
Performers may need to know venue location as they could be taking more then one booking on the night etc.
You should start locking in contracts around 8 - 12 months from your wedding date for major vendors. Keep in mind that brides are booking their weddings sooner and sooner, sometimes up to 1.5 - 2 years out, so definitely give your preferred list of vendors a call as soon as you can to check for availability.
From experience good vendors are being booked out from atleast 1 - 1.5years ahead.
We are not saying that none of the vendors or venues will be available just months before your special day but we will strongly recommend advance booking to avoid significant stress.
Friends, we have a trusted list of vendors who we work with regularly and would love to assist you sourcing them if you need assistance from the MR MC Team.