The meaning of 'deacon' is 'servant'......the diaconate is often seen in that light, as incarnating the serving Christ in the midst of the Church, or as being the example of Christian service in the midst of the community. When I did some research on the diaconate a couple of years ago, I found some interesting evidence that showed that the deacon is sometimes seen as being the 'ultimate layman', in terms of providing this image and realilty of Christian service to the community. I find that, because of this, having active deacons in parishes is a great way to make the laity feel more included in the way the parish is run. It just seems that deacons are more kind of like 'people's clergy', in a way.
Deacons may be involved in running administrative arms of church business and in visiting people in the parish, as they were in the patristic period of the Church. Or their roles might be a good deal less defined. In Slavic Churches, they have tended to be reduced to a kind of 'liturgical ornament' and viewed by people as being 'little priests', which is unfortunate, since the charism given to deacons is quite different from that given to priests. Many men become deacons and have no intention of ever becoming a priest. The diaconate is one of the three 'major orders' of clergy in the Church. Most people probably serve as a reader or subdeacon for some time before becoming a deacon, but although one has to pass throught these two 'minor orders' before becoming a deacon, there is no hard and fast rule about how much time you have to be a reader or subdeacon, and some men are ordained to the diaconate on the same day that they are tonsured a reader and blessed as a subdeacon. Some kind of higher theological education is usually required before one is ordained deacon, depending on the requirements of your jurisdiciton/bishop.
The liturgical role of the deacon is certainly important, but the whole minsterial function of the diaconate is something that needs to be reinvigorated. It is a 'full and equal order', one that is really necessary to the healthy functioning of the Church.