The following articles are all about tuning and the bass guitar. Knowing how to tune is essential, and the more you understand about tuning, the better. Tuning isn't hard, but you have to learn to do it. There are only a few pitfalls you might encounter...
How to Tune a Bass Guitar
Bass tuning lesson. Tune that bass up right!
How to Tune a Bass with Fretted Notes
Bass tuning lesson - tuning a bass to itself with fretted notes.
Tune a Bass Guitar with Bass Harmonics
Bass tuning lesson - tuning a bass using bass harmonics.
Bass Tuners Guide
Guide to electronic bass tuners.
Why Does My Bass Go Out of Tune?
Common causes for going out of tune.
Bass Guitar Tunings
Index of standard tunings for 4-, 5-, and 6-string basses.
Altered Bass Tunings
Common non-standard tunings for 4-, 5- and 6-string bass guitar.