I need to do a few joints in work surfaces, a couple of them right angles.
Any advice on the way to do these joints would be greatly appreciated. I
understand the principal of the long screw bolts and assume that I router
out the grooves for these. My main concern is the cutting of the work
surface

a) can I use a circular saw?

b) for a 600mm surface at right angles do I cut a straight line for , say,
580mm and then a 45 degree cut for the remainder?

c) in addition to the bolts pulling the surfaces together I have also seen
biscuit joins in some situations - how important is this?