Unless you are warming up a wine, holding your wine by its bowl is generally not advised. Some red wine glasses don't even have a stem for this reason. How you hold you wine glass is obviously up to you but there are some things that others judge you on and things that make drinking the wine more pleasurable. However, it seems obvious that when serving a Champagne or sweet wine at a lower temperature, holding the glass by its bowl and warming it with your hands is not the most appropriate course of action, instead hold it by its stem. Let it sit between your fingers with a loose grasp. Having fingerprints around your glass makes it look dirty and can ruin how nice the wine looks in the glass but Lipstick is always tolerated as long as they aren't the ones cleaning it off at the end of the night.