Carcassonne Game

On Sunday our friends brought round the game Carcassonne that we had bought then for a recent birthday. It was great fun.
The play is not complicated. When it is your turn, you draw a card from the bag, and place it adjoining others on the table, then, if you want to, you place one of your free pieces on it. What gets complicated is the scoring, and the strategy.
The play continues until all the cards have been played. Then the points are totted up, and the player with most is the winner. Some of the points are awarded during play, and others are scored at the end.
Each of the square cards has four sides, surprisingly. These are either city, field, or road. When a card is placed each card it touches must have matching edges. Points are awarded during play when a city or road is completed. Points are awarded for fields and incomplete cities and roads at the end of play.
A piece with some city has a wall between the city and the field.  A city is bordered by wall and open sides. When there are no open sides and walls all join up, the city is complete. A piece may have 2 or 3 edges with city, useful for extending an existing city, or just one edge, useful for completing a city. A completed city can have just two pieces, or many. Some pieces have shields, which earn points, or other symbols which earn cards that may earn points at the end.
Roads all run in the fields, never in the cities. They terminate at cities, and they terminate at cross roads. A road is completed when it terminates at both ends. On the way it may run straight or turn corners.
A field is bounded by cities, roads and open sides.  There is no concept of a completed field, and points are awarded at the end rather than during play. Some pieces have four field sides, and a priory on it. This earns points for each of the eight adjoining pieces that are put in place.
You lay claim to a city road or field by placing one of your men in it.You can only place a man on a piece that you have just played. You can only lay claim to a city road or field that does not already belong to someone. That does not mean that no more than one person can own it, as two incomplete cities, each owned by different players may become joined, in which case the each own the city, and are awarded points when it is completed.
After placing a piece, you can put a man on the piece. If the piece has city and and road, you might put the man in the city, or on the road, or in one of the two fields on either side of the road, or you may chose not to place a man at all.
You have a limited number of men. Men placed in a field are there for the duration, but those placed on a road or city will get returned to you when the road or city is complete. As well as the men you have one pig, and one worker. You can place your pig in a field that you already own, and you get 5 instead of 4 points for each complete city in the field at the end of the game.  You can place the worker in any city or road that you already own. Subsequently, when you extend or complete that city or road, you have an extra turn. When the city or road is completed, the worker is returned to you with the man.
Two points are awarded for each piece being part of a completed city or road, and one point if it is incomplete at the end. There are also 2 or 1 point for each city piece with a shield.  A field is awarded 4 points for each completed city it borders, or 5 if there is a a pig as well as a man.  There are bonus points for having the most barrels and cotton collected when cities are completed.
So, do you place your men on cities fields or roads? Do you complete the city you own, or play the card elsewhere in the hope of extending the city later? I am looking forward to playing again to discover what kind of play does best.