Useful Advice for the Amateur Red Wine/Port Fancier

When should wine be decanted?

Well I've never known nor cared until recently but I've decided to relook at Reds as I always enjoyed them so I took a trip around Google to find out. Unsurprisingly there is a multitude of advice and video (god I hate how to video's) but I found this. Easy read and simple enough to do.

I also found this, the decanter I got for my 21st birthday which has never been used...until now. 

"Decanting wine has a practical purpose but is frequently regarded as mere affectation. Do you decant, and if so, what?

As if the stress of getting Christmas lunch on the table were not enough, there's also that last minute panic of wondering whether anything needs to be decanted. If you do, you're not alone. Few aspects of wine service are more misunderstood. Decanting is probably as often performed unnecessarily on wines that don't need it as omitted (possibly for reasons of embarrassment) for wines that do.
The most obvious reason to decant is that the wine has thrown a deposit, and that's really only likely with vintage or crusted ports and aged unfiltered reds. For the process to work effectively the bottle needs to have been upright for several hours, then be carefully poured into the decanter in front of a light (traditionally a candle) so you can see as the sediment inches towards the neck. You need to do this in a single movement so that it doesn't fall back and get mixed up with the wine again.
You may also want to get some air into a wine that smells slightly stinky - there are more of these around given the growing popularity of natural wines made with no or very little sulphur - or full-bodied young reds that need a bit of aeration to mellow over-aggressive tannins. You might even want to decant a full-bodied white if you feel it's tasting a bit funky or not showing at its best. When deprived of oxygen wines can develop strange aromas. If they get worse after decanting the wine is probably corked.
How far ahead to decant depends on the wine. it may simply be a question of getting a bit of air into it, in which case simply decanting before you pour will do the trick (much more effective than pulling the cork and leaving the bottle open for an hour or so).
Wines you don't want to decant too far ahead - or at all - are fragile old reds which might fall apart once exposed to air, most ports (you don't need to decant a late bottled vintage or a tawny, for example) or crisp dry fino or manzanilla sherries, which should be served chilled from the fridge - however much that may horrify elderly relatives.
Decanters don't need to be expensive cut glass crystal heirlooms. We've picked most of ours up from charity shops. You can even use a jug. If you're embarrassed by the whole process you can simply double decant: pour the wine into a jug and from the jug back into the bottle (rinsed if the wine has thrown a deposit).
The ideal shape, if you're looking for presents, is one with a wide base like this which gives you plenty of room to swirl the wine - gently - around. And which actually looks quite stylish on the table.
Which, if any, wines might you decant, or would you feel self-conscious about doing it in front of family and friends?"

Fiona Beckett-The Guardian