Wine is often the beverage of choice at a dinner party, yet frequently the host, as well as the guests, do not have a basic knowledge of wine etiquette & protocol. 
The ritual of wine-tasting involves five senses:

The sound  - wine being poured into the glass
The look - the color and clarity of the wine
The smell -  released as the wine swirls in the glass
The taste - the delicious experience in the mouth
The feel - the weight of the wine on the palate
The four steps of tasting wine:

Ordering wine:

Ordering a bottle of wine at a fine restaurant can be an intimidating experience, particularly when entertaining important guests.

When the wine steward brings the bottle, check the label to be sure it is the exact wine that was ordered.

The wine steward should know if the wine needs decanting.  Older red wines with sediment in the bottle should be decanted.  This also allows more air to come in contact with the wine which releases the bouquet.

Feel the cork after the wine is opened.  Check for moistness, which is one way to determine whether or not the wine has been properly stored.  A cork that is too dry or damaged will let air into the bottle and damage the wine.

Smell the cork to make sure there is no unpleasant odor.   A hint of vinegar will indicate the wine has gone bad.

The first taste is offered to the host/hostess, who will take a sip and indicate approval or disapproval.  The host/hostess is served last, after all the guests have been served.   

Note: There is a difference between something being wrong with a wine and a wine not meeting your expectations. Before sending back a bottle, be sure you know the difference between the two.  It is perfectly acceptable to refuse a wine that has gone bad.

Holding a wine glass:

Why does everyone make such an issue of holding a wine glass properly?  You might think that they are just trying to be a wine snob.  However, the answer is more common sense than snobbery.
One of the important steps in proper wine tasting is "Appearance."  If you hold the wine glass by the bowl, rather than the stem, you will get fingerprints all over the glass.  
When tasting white wines, in addition to fingerprints, you will warm up the properly chilled glass of wine.