Before getting a serious tune these would also be recommended
- new spark plugs (can cause issues with tactrix logging if old)
-new fuel filter, for consistent and maximised results ($65 from USA)
-new/clean air filter, just not filthy
-battery not ancient (5 years is ancient), can cause logging/tactrix connection problems
If while "write to ecu" flashing the ecu fails - do not turn ignition off, as benny said. Instead try to flash the tune again. If a "test write" flash fails - it's safe to turn ignition off, if needed, as nothing was changed.
Lastly - if your finished tune causes any issues like boost spikes or funny noises or knock showing up on LV - tell your tuner! It's all fixable and should be addressed Asap. Allow for a bit of driving, say a week or two, to judge a tune - problems may appear where before there were none. Hence why dyno+road tunes are superior - they should take a while and address everryyyyyyything.
Sorry if I repeated some stuff benny