Firstly, welcome Athomus.
That's quite an ambitious undertaking you are embarking on. good luck.
Since you have mentioned you are using TFN, Timetales and the Ultimate Timeline on there are excellent resources. Also dont forget the CUSWE(Unofficial SW Encyclopedia)
The dark horse website also has a comics specific timeline.
As far as do's and donts:
*Seeing the is pre bane, you arent restricted by the rule of two
*Mandalorians are mercenaries by this era, not a warrior race.
*Try stick to SW naming styles. Coming up with a cool name is important for a good story. The best characters always have cool names - Mara Jade, Talon Karrde etc
*No clones or superweapons !
*Feel free to include a character of the same species as yoda, but perhaps make him a bit different to yoda and vrook from KOTOR. for example, a younger more reckless one !
*Be sure you know what "sith" is defined as for this time period. If its not specified, keep it within the parameters of what preceded(the sith army - moreso a military class) and leading up to and beyond bane - an outlook focussing on gaining power through use of the dark side of the force
*have a droid character - they always provide a device for comic relief and stating the obvious, just like 3po and HK-47
*keep chapters short ! I think alot of readers hate long chapters !
*hutts and wookies !
*consider the timing of the story arc. Are you just running it in a linear fashion, are their overlapping arcs, flashbacks ?? All these have their uses depending on what you are trying to achieve.
*Galctic Basic shouldnt include words from earth that are clearly from an earth foreign language.eg. "attack pattern delta" or "i'll meet you at he rendez-vous" These were used in the films but just seem out of place when you think about it
*have someone say "I have a bad feeling about this"
*listen to the sw soundtrack when you write...keep you in the right frame of mind !