Hi Mike
I'm having quite a good experience with live plants at present - if you use sand as a substrate, bury the roots into this and then put some big stones on to weigh them down, it seems to really do the trick.
Also (and I know this will seem like common sense to everyone, but I didn't do it at first!!!), don't put the plants in the corners of your tank where they're not directly under the light.
I have the lights on a timer, so they come on for 3 hours every night - need them on for the plants to survive, but don't want them on too long, as axies don't have eyelids, so don't like bright light - for this same reason, ensure you have a couple of hiding places, where your axie can go to shelter from the light.
I have found one plant absolutely great, really easy to grow and it keeps growing new shoots all the time - it's threatening to engulf my tank!! Also, it's really common and quite cheap, they sell it at most aquarium/garden shops - but I don't what it's called! I'll post the link with pics of my tank, so you can see the plant I'm on about. :happy:
Cheers
Zoe x
http://www.caudata.org/forum/showthread.php?t=61435