Generally speaking:
Saturdays are fairly slow, especially before 1pm, many of the scheduled flights operate "daily except Saturday". Sundays are better but still not as busy as weekdays for scheduled traffic, although charter airlines are much more evident at weekends, increasingly so as we enter the summer season with the likes of TCX, MON, BY, AMM, MYT etc all plentiful.
Weekdays are busy, especially mornings and evenings, in terms of days- most scheduled services operate every weekday at least, so it doesnt make too much difference to be honest. Try looking at
www.ringwayreports.co.uk or
www.tasmanchester.com for details of specific movements, airlines such as AF, LH, BA, SQ, AA, CO, EK all operate daily. In terms of aircraft type on specific services, there is very little variation day to day, airlines tend to retain the same type on a specific service- the only exception I can think of is BA's London Heathrow service which operates 737's, 757's, A319's and A320's seemingly randomly!
Enjoy yourself, we've had loads of new services at MAN recently, Hapag Lloyd Express, Qatar, China Airlines Cargo etc
Cheers
Landing_24R
By the way, the Aviation Society produces a timetable called, "Flightcheck" which details all the movements expected. It's produced monthly, you can buy a copy in WH Smiths inside the terminals or at the shops in the spotting areas.