This is number 10 for me, it's as near as ideal a festival for me. So what I've learnt in this time...
It's in the middle of nowhere, so a city boy like me was a bit unprepared for that the first time. If coming by public transport then in previous years Festival Republic would organise a bus to pick up all volunteers (crew only so not publicised to festival-goers) on Tues/Weds, and Mon afternoon if doing the final shift. This goes from Halesworth. Hotbox should be passing on this year's arrangement soon so keep an eye on the site for news. If travelling outside this time then pre-booking a taxi is advised as it's a tiny station with no rank.
Again, because of the remoteness, supermarkets are far away. There's some in Halesworth, Beccles and Southwold. A shuttle bus operates Friday to Sunday to Southwold (which has a beach for a day trip!). Alternatively there is 'One Degree East' shop on site, about 50% more expensive than the Aldi but convenient.
The briefing pack and on site briefing should cover all points and queries, and you'll have the previous shift and Hotbox supervisors to pass on any role-specific stuff. You should also get a staff handbook which I think is brilliant, so useful yet I've only got one when working Latitude/Leeds - other festivals should take note! All the staff in all the organisations are very helpful - we're all in it together! Shift-wise, the Arena/Pixies work to arena opening/closing hours so may be an option if the night shift is too much.
If you've never been to Latitude before then it's reasonably compact, the crew camp (at the top of the map last year, and it's not on the public map) is about 25 minute's walk from the furthest stage, the Obelisk. Lots of hidden gems so you can do your own pace. There's a Latitude fan's forum at http://latitudefansforum.freeforums.net/ with other festivallers hints and suggestions.
I'd second the comment about the bugs there, as it's by the lake/coast there's loads of 'em and they love bright tents :-( Repellent's a must!