One of my tactics is to pick a stretch of coastline which will offer several places to fish from.
I usually chuck a few casts in an 180deg. arc as much as is possible for 20 min or so and move on.
I move up and down the coast line (this can be a bit tiring and involve a long walk) but it can pay off.
Then at the peak of the season (over time) you will have found "more likely" spots to try, in different areas at different times of the year.
Also keep notes or an album.
You will be amazed at what you forgot about previous trips out over the years.
I tend to fish over rough weedy marks with shallow or not too deep water with plenty of rocks and gullies.. and early and late times of the day.
I can only get out at certain times, so i dont get to pick the best days or tides but it usualy pays off..(just not at the moment!!!)
A seis for me is about 4/5 hours.
Move about and find the fish........
Now .......where are my new golf clubs???