Well, everyone's talking about chorus on a bass, and it's not as popular as a phaser...
IDK about that. Chorus on bass can be heard kind of all over in a lot of different genres.
My approach to most modulation effects in most cases is to set the two knobs (rate and depth) opposite one another. If it's going really fast, it should be really shallow, and if it's really deep, it should go as slowly as possible. As you turn them away from the extremes, they tend to converge on middle of the road, but that's usually too much of one or the other for me. Just a starting point, really, but it has worked well as a rule of thumb for quite a while.
I also tend to stack them in order to get more complex modulations. Like, I'll have a chorus and a phaser in series. A single cyclic effect can get repetitive and boring sometimes, but the interaction of the two out of sync LFOs adds a subtle but important sense of unpredictability.
I mostly end up using ITB plugs for modulation now, but I have always been perfectly happy with my Boss CH1. It's a pretty straight forward, standard sounding chorus, maybe nothing particularly special, but it does have that tone control to add or remove treble from the modulated part of the signal and also that mix knob which gives a different way of calming things down a bit compared to trying to change depth or whatever.
Another cool thing about it is the way it makes the stereo signal: When you plug into the second output, the dry signal goes out there, but is disconnected from the first output, so one side is just the straight dry signal and the other is only the pitch modulated vibrato type sound. This can very easily be exploited to use it as a vibrato on its own, so it's like two pedals in one. My bassist does this all the time, but we figured out that the Mix knob becomes simply a volume for that vibrato signal. We've had troubles in the past where he just wasn't coming through anywhere near as strong as he should. Checked all the cables and even tried troubleshooting a pedal downstream before I realized that knob was most of the way down.
FWIW - In the box I usually end up reaching for Melda's MVibrato and then adjusting Reaper's Wet/Dry mix to taste. I know have they have a Chorus too, but...