The main route for hiking is the Ulster Way that is designed and widely publicised with hikers in mind. My advice is to purchase a guide that details the walks including distances and expected walk time.
Waymarked Walks gives loads of useful information on local walks.

Hints

Tough waterproof boots
Waterproof clothing

My Journeys

I enjoy the occasional hike and thought it may be useful to some if they knew what they were missing.

Walk2 – Giant’s Causeway to Ballintoy Harbor

Walk3 – Glenariff Park Camping

Walk 4 – Knocklayde Mountain

Walk 5 – Lurigethan Mountain

Walk 6 – Moyle Way Stage 1

Walk 7 – Moyle Way Stage 2

More info on this subject to come…