I'd handselect the lumber for even grain and so forth as any knotholes will
seriously weaken the strength of the lumber. Better is to get a better
quality lumber that is used for roofing.
Next is that you don't want to do is to screw the lumber together. Better
is to support the beams so that you could put the shelf together witout
fasteners and it will stand (until some side forces knocks the mess down) by
itself. Screws, bolts and nails, etc. are nice but they shouldn't be doing
the heavy support as they are localized loads and will be in shear which
will quickly crush the wood in the area of the fastener.
"Fancy" joints were used in the old days for a very good reason, they
allowed the jointing of wood without the need for the expensive metal
fasteners of that day. The wood was supported by the joint and nails or
pegs were used to make sure that the odd load didn't pull the joint apart.

--
Bob May
Losing weight is easy! If you ever want to lose weight, eat and drink less.
Works evevery time it is tried!