[mattbrewsbytes]

If there are key critical systems, you want to have some documented plans down to checklists of things to do if there is some sort of emergency. I work in BigCo and having redundancy is nearly mandatory for all of our critical stuff. That may not be affordable for a small business, although if you phrase it in a way that electrical engineers would understand (fail safe like a GFCI interrupt or breaker) they might buy into it for a critical system. Bad things happen and if you can get them back up and running ASAP (e.g. failover to redundant system) and then fix the broken system you'll have less headaches.

Setup version control and use it, it's like having a time machine if you mess something up and need to get back to a working state. Git is all the rage, but Subversion is simple to setup and run and understand. It's just you so having a distributed VCS isn't likely to reap any rewards.

Use an agile approach when delivering features/changes. Build an entire "vertical" of a change like say moving one app from MS Access to a Web UI completely (or whatever you're going to move it to). If you design and develop each layer, like db access, business objects, UI in serial fashion then it will be a longer time before end users can give you feedback. Get that feedback as early an often as possible.