Hiya, I grew up on the mid north coast and I’m pretty familiar with the area so thought I throw in a few comments. I actually put in a few kms on the bike up that way a fortnight ago as well (My parents are still up that way and we spend many a weekend at Forster with them).
SOUTH FROM FORSTER
Heading south from Forster is probably one of the most popular routes. This is the general direction/route of the (old) Foster ironman triathlon as well as the Forster half (every October) so the people out that way are used to seeing bikes on the road. The Forster tri club use the area around Forster Quays for training so you may well see a few other people on bikes out that way.
Here is a map of 50km ride from Forster to Blueys/Boomerang Beach and back. Near to where the riders turned around here there is a small group of shops for your coffee/water/sports drink refill needs:
http://www.bikely.com/maps/bike-path/Forster-to-Blueys-Beach-and-backIf you want to make it longer in this direction then the ride out towards Buladelah is pretty much the only option (many of the other side roads are in poor condition/not very long/unsealed). I’ve never been as far a Buladelah (or Pacific Hwy) on the bike, but I would suggest that its reasonably safe except for the last 10kms before you hit the highway which is hilly/windy and narrow (and is hit pretty hard by hoons/motorcyclists and also carries lots of caravans). There is a good mix of hills and nice flat country road sections out here plus some good views of Smiths Lake etc.
http://www.bikely.com/maps/bike-path/Bulahdelah-to-TuncurryNORTH FROM TUNCURRY
The rides north from Tuncurry essentially follow the Lakes Way.
You have a couple of options, go towards Blackhead/Hallidays Point/Diamond Beach (and do a bit of a tour) or head towards Taree.
If you are heading towards Taree I’d take the Failford Road out to to the Highway (turn left near the ‘Ton-O-Fun’ park) as shown in this map as I don't like the bit of road between the blackhead turn-off and the highway - I know a few cyclists who avoid it):
http://www.bikely.com/maps/bike-path/Forster-TareeFor a good day on the bike you could always do the Lakes Way Grand Tour (copyright AndyTheMan 2011

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Tuncurry – Lakes way to Failford – Failford Road to Pacific Highway - South on the Hihgway to Buladelah – Ruturn to Forster via Lakes Way/Blueys Beach/Boomerang.
At a guess it would be about a 150-170kms circuit
There are lots of nice little rides around town as well – when I was up there I was up early and did Forster Main Beach, around all the lookouts and ended up at One Mile Beach as a 15 min warm up ......afte which time I felt so relaxed I started looking for a coffee shop anyway...
Be aware that Foster is INSANE at Christmas time in terms of traffic and people, so I'd be looking at very early rides to get away from the traffic. There are lots of tourists and people driving around to the beaches, towing boats and generally not knowing where they are going so be careful - its a proper mad house up there over the school hols!
Have fun!
Also, another thumbs up to the guy running Forster Cycles where the old fruit shop used to be in Forster – had some really good stuff in there and was super nice!