The first step is to look at the wine in your glass.
What color is it? That is the first question I ask myself. The color can give you a hint as to what you will be tasting. For whites I use a 3 color scale, the palest being Straw, then Yellow, then Golden. For red wines, I use a 3 color scale as well, Garnet, Ruby, and Purple. I also tilt the glass at a 45 degree angle to look at the color of the rim.
Can you see through it? This can also give you a hint as to what kind of wine is present (in a blind tasting), specifically red wine. I will use an intensity scale of low, medium-, medium, medium+, or high and tilt the glass at a 45 degree angle.
Is it cloudy? This is a simple yes or no. Cloudiness in wine can denote contaminants, sediment, or oxidization.
How viscous is the wine? When you swirl the wine in the glass, watch the liquid on the side of the glass. How fast does the liquid run back down? Viscosity shows what kind of body or weight there is to the wine. It can be thin like water, which would be low viscosity...or high like milk.
The next step in judging wine is to smell it. When you first pour the wine, it will smell differently than if you decant it for an hour and then pour it into your glass. Air opens the wine up allowing the aromas to show through more clearly. Hold the wine glass up and put your whole nose inside, thats the best way to really smell it.
What do you smell? When I first started out smelling wine, it was hard to pick out particular smells. But as I practiced, it became easier. I also use this aroma wheel to pinpoint certain smells that are familiar but I don't necessarily recall.