| Okay, first thing you want to check is the "relief" of the neck.
You can do this by fretting the E string on the 1st and 15th frets simultaneously (one with each hand). Now see how much space there is between the bottom of the string and the 6th-8th frets. Generally, you want about a business card's thickness worth of space (although some basses require more and some work better with less).
So, if your son's ESP has more than a business card's thickness, you want to tighten the truss rod.
Before you adjust the rod
1) Mark the rod's adjustment nut with a felt pen to note where you started. If you desire, you can remove the adjustment nut (after you marked it) to clean and lubricate its threads (3 in 1 oil works well, but avoid the wood and finish of the bass). Make sure to keep track of the number of turns it takes to get the nut off, so you can turn it back to its starting point.
2) Then, loosen the rod just a tiny bit first to make sure that it's not already as tight as it can go. Then you can begin tightening.
3) Always turn the truss rod in small increments, 1/16-1/8 of a turn at a time, checking the relief in between increments.
Never force the rod!.
Once you have tightened the rod to adjust the relief, play all the strings on all the frets to check for fretbuzz. If the bass buzzes badly, back the rod off in small increments until the buzz disappears.
If the bass has less than the business card's amount of relief and the frets don't buzz, the truss rod is already setup right, you don't have to adjust it.
Next, you can raise or lower the action (height of the strings) at the saddles. Make sure the strings match the radius of the fretboard when you are done adjusting the saddles (sight down the neck to compare the radius of the strings to the radius of the fretboard, eyeballing it will be close enough, you don't have to be perfectly exact here).
When lowering a saddle, turn its height adjustment screw(s) 1/2 to 1 full turn at a time, then play all the frets for that string, checking for buzz. As soon as the string gets fretbuzz on any fret(s), back the saddle off just a litte until it doesn't buzz; that string will then be as low as it can go (you have optimized its action).
Next, you need to check the bass' intonation.
You'll need a decent, preferably chromatic tuner for this job. The cheapest I'd recommend going is a $20 Korg CA-30. The higher the accuracy of the tuner, the better the intonation.
Plug the tuner into the bass and turn on the neck pickup only.
Make sure the bass is tuned to pitch.
Play the open E (or harmonic at the 12th fret), then play the E fretted at the 12th fret. If the fretted note is sharp compared to the open/harmonic E, you'll need to adjust the saddle backwards (away from the neck; be careful not to bend the string when fretting).
(You can find the length/intonation adjustment screws for the saddles at the back of the bridge).
If the fretted note is flat in comparison, you'll need to adjust the saddle towards the neck.
After adjusting the saddles slightly forwards or back, re-tune the bass and re-check the intonation. Repeat until the open/harmonic E and the 12th fret E are both in tune. Repeat for each string.
Finally, you can adjust the pickup height (if the ESP has height-adjustable pickups). Fret the E at the last fret, then raise the pickup until it is 1/16" to 1/8" from the bottom of the string. Repeat for the G-string side.
Thats' about it. I didn't cover any nut adjustments, as they usually require more tools and know-how and on a bass in that price range, the nut should be fine.
Let me know if you have any questions or run into any snags along the way.
Enjoy! | 
