There is a (very) basic model that involves taking into account the position of the moon - the earth rotates on its axis once every 24 hours and the moon rotates the earth in the same direction once every 28 days. The moon pulls on the sea creating a sort of bulge on the side of earth currently facing it, hence high tide - an equal bulge appears the other side and in the middle it's low tide.
The difference each day between the earth's rotation and the moon's is about 50 minutes, hence the tides are delayed by about this much from one day to the next.
Generally speaking, if there's a beach you can tell if the sea is going in or out by looking at how wet the beach is from the sea. If it's a gradual "drying out" then it's probably going out, if it's mainly dry with a sudden wet path near to the sea then it's probably coming in.
Using these two pieces of information you can wait a while, work out when high / low tide is, then estimate with the 50 minute distance rule what it'll be next. However, this will be a very rough estimate and may even be totally wrong!
- The sun also has an effect on the tides, though a lesser effect - but this means when the moon and sun are aligned the pull is greater, generating a spring tide once every 2 weeks. The opposite happens in the same timeframe when they're at right angles, forming a neap tide.
- The speed of waves varies dramatically depending the depth of the ocean and all sorts of other factors, influencing the tides in various places.
- The shape of the continents also affect the waves as they stop / bounce / come under various interference patterns.
- Some places are so enclosed they barely have tides at all, some parts of the Mediterranean have tides of only a few cm.
So in short, the only sure fire way of knowing the tides is to look them up before you go, or have a device that implements the various complex mathematical equations for you. If you absolutely need to make a guess then things like the above are your best bet, but I'd never suggest relying on them.