it depends on the type of material or compounds you separated. but in general polar compounds need polar solvent (water, alcohol, chloroform) and non polar compounds need non polar solvents (hexane, petroleum ether, benzene, toluene). I think that there is no fixed solvent for each test. you must optimize your system to obtain the best results
It is quite simple. Just go through the polarity index of the solvent. In TLC operated as normal phase chromatography, as the polarity increases the retention factor will increase. Hence by controlling polarity, we can get the desired retention. If the Rf value is near to zero, Increase the polarity. If Rf value is near to 1, decrease the polarity.