If the bottle has come straight from your cellar, or wherever you have been keeping it, there is no need to leave it standing upright before decanting.  However if you suspect that the sediment may have been recently disturbed, for example during a bumpy car ride from the wine merchant to your home, it is best to give it some time to settle.   
To avoid any particles of sediment passing from the bottle into the decanter, some people like to decant the wine through some kind of strainer or filter.   Decanting funnels incorporating a metal strainer are useful for this purpose but not essential.  A metal sieve will serve equally well. Very clean muslin or plain white cotton cloth also makes a good filter if available.  Whatever kind of strainer or filter is used, it should be thoroughly rinsed beforehand with hot water, never washed with soap or detergent.  Paper coffee filters should not be used as they affect the taste of the wine, even if thoroughly rinsed.
In reality, no filter or strainer is required if decanting is carried out carefully and gently.  If some particles of sediment do find themselves into the decanter, this is not a major catastrophe.  They are completely harmless and will eventually sink to the bottom of the decanter.
Some older bottles of Vintage Port have a white chalk mark painted on one side of the bottle. This indicates that the bottle has been stored with the white mark uppermost and it is best, although not essential, to hold the bottle in the same position when decanting it.  If there is no chalk mark, hold the bottle with the label uppermost.
To be enjoyed at its best, a bottle of Vintage Port should be drunk on the day that the cork is first drawn, before the delicate and complex aromas which develop in the hours after the bottle is opened begin to fade.
A decanter of mature Vintage Port circulating round the table after a good meal with friends is one of the most sociable and enjoyable of pleasures.
As already explained, a wood-aged Port (Late Bottled Vintage included) does not need to be decanted and can be poured straight from the bottle.