If it's been rainng, ther will be puddles around - I often get some water on my hand and "drip" it into the fuel sample - look for it to sink to the bottom, which tells you the sample is fuel, and not water (kind of what another poster said). Water-paste is another good way to make this check. CAOs even mention the unreliable nature of sensory (sight/smell/touch) judgements on fuel samples...
If you get into weather related trouble, the tendancy is to want to get on the ground. This can lead to rash or ill-considered actions. Be patient, remain calm whilst considering your options (and your endurance, obviously). There are good books on this stuff. "Weather Flying" by Buck is one. Some good stuff in there (but large parts are also orientated strongly towards North America). Still, check it out. That stuff will serve you well now, and also as you move into IFR ops too.
CR.