The Courts Service have published a useful guide which may be accessed here:
[broken link removed]
(If the link does not work just google: courts service registering a lis pendens.)
Whilst they are easy to register, the process should only be used for genuine claims, as any interested party can apply to courts to have the Lis Pendens lifted and obtain an order for costs against the party who registered the Lis Pendens in the first place.
Whilst a Lis Pendens registration can "sterilise" the property and detract purchasers from buying the property, I have seen cases where purchasers completed the purchase on the basis that they knew the Lis Pendens was frivolous and had no merit.
Jim Stafford