#1
What do people usually do as far as dual tracking goes with bass guitars? Do the dual track them and then pan one full right and the other full left like the do with guitars? Or do they sometime record one track and set it dead center?
#2
DI to one track and record from a bass amp on the second track. Your DI will have a bit more top end and a little less bass (but you can normally EQ more out of it) and the microphone will pick up tonnes of sub. Find a balence between them (I usually end up sticking with the DI) and keep them panned in the middle.
#3
Where have you seen/who told you to double-track bass?! Apart from in very rare circumstances, I can't see why anyone would want to do so.

I often have three or four bass tracks in a mix (or double/triple that if the bass was recorded in several parts on different tracks) but they are always copied tracks of the original playing at the same time, with just different treatments.

On the (preferable) occasion I get to mic a nice bass amp I would usually end up with the following:

1 x Clean DI (processed with pretty heavy compression, and maybe some EQ to accentuate the low end).
1 x Mic'd track (lighter compression than the other tracks, shouldn't need much EQ other than HPF at an appropriate point to increase headroom and not get too bass-heavy in clubs/systems with subs)
1 x 'LPF bass' (EQ'd to cut everything above, say, 500Hz or something so I can compress the living fcuk out of the low end on this and get the DI'd tracks nice and heavy)
1x 'gritty' bass (another copy of DI, with a distortion/overdrive added to sit very low and gel to the guitars better)
Hey, look. Sigs are back.
#4
Double-tracking bass? NO no no no no.


One take, straight down the middle, no fancy stuff.

It's very common to have have two tracks, one DI and one mic'd (so you can blend them to get a nice balanced tone) but playing the same part twice would have no benefit whatsoever and would make it sound worse.