I only recently discovered Bass Musician Magazine. It's an online magazine to which Contrabass Conversations’ Jason Heath contributes. Overall, I think it's pretty good, although you can't really trust or expect great things from everything you read online. While many of the technical articles are largely targeted towards beginners, there are some interesting articles on avoiding injuries by Randy Kertz and some good articles giving tips for practicing. What I particularly liked was on the idea of "doubling" by Adam Nitti. His general theme is on increasing your speed. The typical way this is done is by setting your metronome and slowly increasing the tempo to build up speed (he calls this the "metronomic ladder"). Nitti's suggestion is to play a piece (say a scale or arpeggio) at a given speed three times and then, without changing the metronome, doubling the speed for the fourth repetition. For example, play a scale three times as eighth notes in the fourth time at sixteenth notes. Eventually, as you get better at playing the piece at the initial tempo, you can increase the metronome tempo or increase the number of times you play it at the double to speed. In his words
"the reason this approach is so effective is because it shocked your system at the plank twice as fast momentarily under focused concentration and attention to detail because you are only playing a single repetition at double-speed unit not become overwhelmed by the faster tempo, and thereby have a much higher success rate with respect to your conditioning."
I've been trying this technique with my warm-up exercises and that without it very useful.
Another tip I came across is in Margret Elson's "Passionate Practice." The tip (in full detail on page 51 of her book) is to take a piece your trying to learn, get in a relaxed state, and then play only the first bar plus the following downbeat. After having done this get back into a relaxed state and play the second bar plus the following dounbeat. Stop again get into a relaxed state and continue with the subsequent bars or groups of bars (e.g., play four bars plus the following downbeat). I found this technique very useful on the more difficult pieces I'm trying to learn. The technique made me focus on just getting a small part of music down. Oftentimes, I get overwhelmed when I try to play a piece. This technique has allowed me away to break the piece into smaller chunks which I can get my head around and then assemble into the full piece. That said, I don't follow this technique religiously. I only really use it on parts work by myself getting tripped up.
Just as a note, I like Elson's book. I've read reviews of it that haven't been very good, although a lot of their criticisms are well-founded. She talks about putting yourself in a relaxed/alert state using a "calming light" exercise. She also talks about positioning your hands in "puppy dog position" and using a "magic carpet" to raise your hands to your instrument. If you can get beyond this terminology (which I feel compromises or trivializes what she's trying to say), I think the book has a lot of nice lessons and tips on how to prepare yourself for learning and performing.