NCN1 doesn't go through Caistor. The closest it gets to Caistor is Swallow or Thoresway.
Now depending on how much you like hills, there are a few choices.
Whatever you do, I'd avoid the A46 like the plauge as it is a very busy narrow road, frequented, it seems, by unsypathetic motorists.
Take Whitegate Hill road out of Caistor to where it meets the B1225 (AKA Caistor High Street) and turn right onto the B1225 until after a short distance you get to a crossroads. Here you have 3 choices as I see it.
1. The scenic and hilly route.
At the crossroads turn left towards Rothwell (pronounced Rovvel by us yeller bellies). Turn right in Rothwell and head towards Thoresway (pronounced Forzer). Here you pick up the NCN1 turning right. Follow the NCN signs (which are mostly well maintained and visible), taking you back over the B1225, down Walesby Hill, through Walesby. The onto my home town of Market Rasen, where you straight over at the lights down Linwood Road to Linwood. Turn right as you leave the village of Linwood.
2. The even hillier route.
At the crossroads turn right towards Nettleton (where my dad used to work in an ironstone mine). In Nettleton turn left and go up Normanby (pronounced Norranby) Road and up a quite steep hill past a carpark on you left, then past Acre House farm and onto Normanby-le-Wold, passing the Claxby radar station (AKA the golf ball for reasons that will become evident after you see it). Here go down Normanby Hill (steep!) into Claxby. Carry on straight towards the A46. Turn left onto the A46 (care!) and then immediately right onto Osgodby Low Road towards Osgodby. Before you get to Osgodby take the first left into Sand Lane (A). Follow this, turning right then left and the junction towards Middle Rasen. Here turn left into Low Church Road. Go through the village, past the bowling green until you reach the main A46/A631 road. Here go straight over into Mill Lane. Carry on over the railway bridge (Buslingthorpe bridge). Here you pick up the NCN1 as it leaves Linwood.
3. Very few hills route.
Out of Caistor, take the North Kelsey Road. After some time you will come to a crossroads. Turn left (before you get to the pub) and go over Smithfields level crossing. Follow this until you come to a T junction. Turn left. This isn't a main road, but it does get quite busy so be aware. Follow this a short way until you get to Moortown crossroads. Here turn right towards South Kelsey. On a sharp right hand bend, go straight on (signposted Thorton-le-Moor). Take the first left turn to North Owersby. At the next T junction turn left to Osgodby. After leaving Osgodby, take the second left (Sand Lane) and proceed as route 2 from (A).
Any on the above routes will pick up the NCN as it leaves Linwood. You will cross the railway line twice over level crossings until you reach Wickenby (site of a Lancaster bomber base in WW2). Turn right in Wickenby and head to Snelland, where you turn right and cross over another level crossing. Keep on the main drag (left) to Stainton-by-Langworth (passing the rather nice Reasby hall where my mum used to work in service many years ago). Turn right and head to Scothern (where my mum now lives in a nursing home). Pass the church and head to Nettleham, where you turn right down Deepdale Lane past the police HQ. Here you pick up the cyclepath that runs alongside the A46 into north Lincoln. Go straight over at the RaB and head into Lincoln down Nettleham Road (cycle path available). Follow Nettleham Road until you pass the Lincoln Hotel on your left. Here you go straight on through Priorygate Arch (part of the old roman city walls) and past the glorious cathedral on your right. Go past Pottergate arch and out onto Lindum Road (A15). Go down Lindum Hill. Here it gets a bit messy. Go down the hill and onto the dual carriageway that is Broadgate. After a few hundred metres (crossing over the river Witham), turn left into Pelham Street (passing my workplace Siemens on your left). Here you pass under the dual carraigeway (Pelham Bridge) and into St Mary's Street. Pass the railway station on your left / bus station on your right. At the lights, go straight over into Wigford Way. After a short while you will see the Odean cinema on your left. Get off your bike here onto the path and turning 180 degrees, walk a short distance down to the Brayford Pool (passing the Royal William V pub). Here you can mount up again and cycle alongside the Brayford Pool (lake) down Brayford Wharf north. After you pass the Holiday Inn on your right, you go under the university bridge and from there you pick up NCN64. There is a very short section (50m or so just as you pass Foss Street) where you have to (officially) get off and walk (but most people don't). From then on follow the NCN64 signs following the Fossdyke navigation, past the Woodcocks pub and out to the bypass. Here you get routed through the Woodcocks car park. Careful as this covered in very deep and lose gravel / pebbles. You go through a concrete tunnel under the bypass and immedately turn left onto the start on the cyclepath. You zig-zag up onto the side of the bypass road, and then over the Fossdyke and railway, then down the cyclepath on the other side and onwards to Skellingthorpe and Jerusalem.
Hope this helps.
If I were doing it, I'd take route 1 :-).
