Top tips:

• Ladders, lofts and roofs present obvious hazards. If in any doubt about your safety, ask a reputable roofing company for a survey
• Inspect your roof at least once a year from ground level. It may be helpful to use binoculars, or to view from a neighbouring property
• Looking from inside the loft may show daylight, a possible sign of missing or damaged coverings or flashings
• Debris on the ground might be from slates/tiles. This is a potentially unsafe condition that needs prompt checking
• Failing to replace even one missing tile or slate can cause water damage to the roof structure. This will be much more expensive to put right than having a tile replaced!
• Hip ridges and flashings can become detached in windy weather. Look in gutters and gullies for signs of mortar
• Moss can block gutters, and may also damage the roof covering during frosty weather. Careful removal is advisable

Much more information is available here.