Learn How to Hold a Bass Guitar
For some reason over the years, it has become common place for bassists and guitarists to wear overly large straps to the point that their instrument might be literally hanging at their knees and they have to bend over just to reach it. While plenty of people become quite proficient at holding a bass like this (one of Alice Cooper’s touring bassists wears his bass so low that his microphone is only about three feet off the ground because of how far he is hunched over), it simply makes playing more difficult than a more comfortable height.
While it is worthwhile for some to have the apparently “cool” kneecap level bass, most people probably would rather have it positioned so that they can play without having to compensate for a weird bass hold.
Unless you really, really want an oddly shaped bass, always go for the more normal shaped designs. The odd shapes can sometimes force the player to hold it awkwardly, no matter how well they normally hold the bass.
Bear in mind that not all odd shapes are difficult to hold, so at least try them out to see if that is the case. Some Flying-V designs actually are quite easy to play while sitting, while other slightly different ones are near impossible to play other than standing.
Playing While Sitting
Sitting is quite common when learning how to play bass guitar. The best case scenario would be to use a chair without arms, that could get in the way, otherwise at least try to sit in a way where the arms are at least out of the way. Sitting up straight also is important to maximizing your range of motion, since sitting hunched over does impact how your shoulder moves. Unless you have an oddly shaped bass, which can sometimes be near impossible to sit with comfortably, you generally want to have it rest on your fretting hand leg, with the body mostly being held between your legs.
This will generally give the best neck access in a comfortable way. However, switching to the picking hand leg can help if you can’t reach the lower frets, though you likely will not be able to use much of the higher frets in this position. Since bass lines generally revolve around the lower frets, being able to access those is generally the most important. Usually you want to tilt the neck up fairly high to minimize how far to side you need to reach, but this will vary from person to person.
Playing While Standing
In most performance situations, standing is more common than not for a bass player, so learning to play bass while standing is quite important. One important thing is to stand up straight, because as with sitting, better posture improves the range of motion of the shoulder. Also keep the strap length to a reasonable level.
A good rule of thumb is trying to position the strap so the bass is about the same level when you stand as when you sit. However, play around with it since the range of motion does change a little bit when standing. In addition, even you mostly practice your bass guitar lessons while sitting, be sure that you can still do them while standing. It isn’t very common for bass guitarists to sit while performing, so making sure you can still effectively play while standing is important.