These two videos describe how to make adjustments to your gears:
Set your derailleur limits . Note this video makes no mention of the 'half cock' position that some bikes use to allow the full range of rear gears without the chain rubbing against the front derailleur. If your bike has that feature, you'll need to use it to check all combinations of gear positions work OK.
Clearest instructions I have ever seen on this task.
Will now see if they work on my bike.
Thanks
Yes, very clear instructions indeed - I've bookmarked these videos as they are very good. For those with indexing problems, here is a link to a PDF document titled "100 Causes of Bad Shifting"
http://www.bikebrothers.no/files/files/Manualer/01_100_Causes_of_Bad_Shifting.pdf
Excellent video content, and well constructed with links to related topics.
The only line I'd disagree with is "If your inner or outer cables are dirty then replace them" ... Obviously this will work and may be best practice in a shop where time is money, but there's nothing wrong with removing the inner, thoroughly cleaning everything, lubricating, and reassembling if you are doing it yourself (and if that doesn't solve the problem get new cables).
100 ways for derailleurs to go wrong ... blimey!! come back Sturmey Archer, all is forgiven 😉