I would emphasize paying strict attention to tides and currents. These are often phenomenon not understood by lake sailors bring their boats onto coastal waters. The tides and tidal currents can pose serious dangers to those not understanding them.
For instance, anchoring out, it is easy to forget to leave enough rode out to accommodate the tidal range. That can leave you with far less scope than you expect. As an example: If you're anchored in 10' of water, and have three feet from the bow roller to the water, and it is low tide with a tidal range of 7'. Letting out 91' of rode, which should give you a 7:1 scope, since 7*13=91, at high tide will leave you with a scope of less than 5:1, since 91/20=4.55. If you get caught by a storm with such a short scope, the chance of you dragging anchor is much higher.
Another example is the tidal currents. Trying to make the entrance of a harbor that faces southwest with a southwest wind against a falling tide can be pretty tricky. Trying the same harbor entrance with a rising tide is often much simpler and safer.
The tidal currents can also greatly increase or decrease your SOG. Sailing with the tidal currents can often gain you 2-3 knots of speed over ground, which is very important in a small sailboat. If you're sailing with the tide and can normally sail at 5 knots, you may end up sailing with an SOG of almost 8 knots. If you were to sail against the tide, you might be only making a bit over two knots—slowing your boat's SOG by almost 75%.
