I thought seeing as I'd started a topic on practice, I'd go into a bit more detail into my current routine. It may not be for everyone and it's important to remember that as with most art-forms there's no right or wrong...what works for some doesn't for others.
For the last 4 or 5 years, I've had certain things be the staple parts of my practice diet, if you like. One of those is what I call my students the 'Spider Exercise', the classic one-finger-per-fret across all strings and in groups of 4 frets all the way up the fretboard. Doesn't matter if you're 8 or 28 (though I'm 3 years shy of that...), this exercise will get you nice and warmed up for some more musically-inspiring practice. Next, is running through the first couple of parts of the Hanon piano exercises book. You can grab this off of Amazon for a few dollars / pounds, and is a series of scale exercises running through different patterns. I tend to pick a few different key centres around the bass to test my fingers with larger and smaller spacings. For example, the first 20 or 30 exercises are all based around a C major scale. I'll run through these in a combination of a G maj scale (3rd fret E string G) and an E major scale (12th fret E string E). Again, doing this pretty much every day is all about increasing dexterity, comfortability around the fretboard and that all important muscle memory. Remember, pretty much every awesome thing that you hear in music, be it a lick, bassline or 160bpm solo, is based on a scale or a collection of scales.
I'll run through a combination of major, melodic and harmonic minor modes. If you're not sure what these are, check them out. If you've ever wondered what the hell some killing cat is playing or how they're playing it, it's a combination of chops and a vast vocabulary gained from extensive knowledge from listening, transcribing and getting their theory down. Modes fall into this category - and don't stop at major modes. Melodic minor modes are the gateway to interesting phrases and soloing!
Next I'll focus on a specific song. Usually a bassline, melody, solo, passage or phrase will have pricked my ears up and I'll have the urge to find out not just HOW to play what I've heard but WHY. If you can work out the why, then you can use the idea in your own context and put your own slant on it. If you only have the how, then you have an idea that isn't relevant to any other piece of music or moment than from where you first heard it, making it pretty much useless except as something to boost your own ego or impress others. Which can sometimes be handy, but that's not the point!
As I said in my very recent blog post, I've been revisiting John Coltrane's solo in 'Moment's Notice'. It's not a bassline, obviously, but many trail-blazers over recent decades have shown that we shouldn't think of ourselves as rooted to the instrument that we play, but as MUSICIANS. Calling myself a bassist is accurate of course but doesn't cover my composing, arranging, or transcribing infuriating-but-legendary saxophone solos. As a bassist I have specific roles and duties at specific times but it doesn't mean I shouldn't be totally prepared for and aware of everything else that's happening around me. Download this and run it through Transcribe or Robick (for iPhone / iPad users), and try and work out some of his solo. It doesn't matter if you don't dig the music, but your skill on the bass will improve because you'll be playing in ways you never thought likely on the instrument.
Other solos I've been working on recently have included a few of Hadrien Feraud's monstrous solos. This guy is a phenomenal player and his harmonic understanding is almost completely unrivalled. Try running 'Natural', 'Rumeurs' or for a more melodic solo, 'Shall we love?' through Transcribe.
Anyway enough rambling from me - have some structure to your shedding sessions, and have your bedrock of material you visit every day - it'll help with your rudiments and prepare you for whatever new challenges you throw yourself into.