I thought I'd ask in here as MTB bikes are more likely to come with a suspension front fork. I've got a hybrid (Spesh Crosstrail) that has an SR Suntour NCX front fork.

Is there any maintenance required for these forks? I can't seem to find anything useful in the manuals that came with the bike.

There was a reference to setting 'sag' that seemed to be quite important.

Setting sag is quite important for ride characteristics.
Too little, and fork becomes stiff an possibly bouncy.
Too much, and fork becomes soft, mushy. May bottom out even at moderate hits.
Most forks in that price range probably go their whole (shortened) life w/o service.

If you ride a lot in dusty/muddy conditions, replacing the scrape rings regularly is a good idea. If these fail you’ll quickly chew up the bushings and maybe even the inner legs.
Particularly for air sprung forks, good seals are important.
Some dirt will always make its way through, so replacing the oil in an oil damped fork is generally a good idea, even If you won’t notice any immediate result.

[MENTION=114951]dabac[/MENTION] - thanks for you input. The bike is going for it's 6-week tune-up service so I'll get the shop to check that the 'sag' is set correctly for me.

Since sag is set with you on the bike, you’ll have to be present for that.
My favourite method is to put a zip tie around the upper fork leg, right against the seal. Then I get on the bike and ride seated on a smooth road for maybe 100 yards.
Then I check how far up the zip tie has been pushed.
25-30% of total travel is a common recommendation.

Apparently it's a while-u-wait service just to re-torque and retension things on the bike, and doesn't take more than 15-20 minutes so I will cycle to the shop and sit on the bike as necessary to get the 'sag' done. I imagine it's a fairly quick process.

Looks like this might be an air fork? Depending on conditions and mileage, I recommend service about every 100 hours. Wipe the dust on the stanchions with a rag frequently.
I don’t know if Suntour has a factory repair shop or not. Your LBS should be able to replace seals and possibly bushings if they need it.