The part of the game that you will find hardest to understand is that concerned with what industries you can build and where you can build them. Once you have mastered this part of the game the rest is relatively simple. I wish there was a quick way to make the rules easier to understand, but I've not come up with one yet. The big problem is that you have to keep a number of factors in mind when building.
You need to make sure the card you play will allow you to build in your intended location. This means making sure the symbols on the card, the counter, and the space are all the same. Industry cards are more complicated to use than Location cards, as you need to trace a connection to one of your other counters via your own canal/rail links. What then makes things doubly confusing is the fact that you may or may not need coal to build. Coal has to be shipped along canals/rails, which means you need to plan carefully.
It probably makes sense to start by building industries that do not require coal, just to get used to the basic mechanics. Don't worry about needing iron to build as this commodity does not require canals or rails to be moved to its final destination.
When you start the game do not try to be too ambitious, keep things simple. Your first action should be to build either a cotton mill or a port. If you build a cotton mill then try to build it as close to Manchester as possible. If you build a port then Liverpool or Preston are good places to start.
To build that cotton mill you are either going to play a Location card, in which case you simply build in that location, or an Industry card. If you use an Industry card then you can build in any location with a cotton mill symbol, as you do not have any other counters on the map yet.
Once you have a counter on the map it's a good idea to build a canal from it. Canals allow you greater flexibility in the use of your Industry cards. They can also earn you a reasonable amount of victory points.
Once you are used to building industries that do not require coal then you can start to build ones that do need coal. You need to plan carefully to make sure you are connected to a source of coal. Ideally this would be your own, but it's not essential. Being close to a port or external location is always good as this gives you the opportunity to buy coal from the Coal Demand track.
With cotton mills you are looking to be connected to a port of some kind. Being connected to your own port counters is the best situation, as when you sell your cotton you can sell it to your own ports.
The more cotton you can sell in a single action the better, as this is a more efficient use of your limited number of actions. However, if you delay selling too long you may find there is no market for your cotton. It helps to get your income up fairly soon as this gives you the opportunity to take a loan without having to go into negative income.
Cotton mills are certainly more profitable than ports. The advantage of ports is that they are cheap to build and never require coal or iron. They should be part of your portfolio of industries but I do not think they are the most important.
Once you have a few cotton mills and ports up and running you may consider going into iron. A good time to build an iron works is when a few cubes have already been taken from the Iron Demand track. This means that you can usually get some of the costs of the building back immediately, and you will also be closer to being able to flip your iron works to its other side.
Coal is not in great demand in the Canal Period. However, once the Rail Period starts it becomes crucial. Try to end the Canal Period with at least one coal mine with coal already on it, (and one that is not going to disappear at the end of the period). Such a mine will act as a centre for you to expand your rail network from in the Rail Period.
Shipyards offer the promise of lots of victory points but are costly to build in terms of money and development actions. You can decide to ignore them and still have a good chance of winning the game. However, if other players are also ignoring shipyards then they can suddenly become a good investment, as you will have no competition for the available build spaces.
You will need to do some development during the game. You want to make sure you start the Rail Period without too many restrictions on what you can build. It's good to have a few Tech Level 2 industries on the board at the end of the Canal Period as these act as centers for you to expand from in the Rail Period. Remember that in the Rail Period you can have more than one counter in a location. The biggest problem you will have with building is getting coal. Being close to an external location or port is good as you can then take coal from the Coal Demand track.
As the cards only have an impact on one of the possible actions you can perform you may wonder why they are in the game at all. There is no simple answer, I just find the game works better with them than without them. The cards do limit where you can build but careful planning will allow you overcome any major limitations. It helps to look at your hand carefully at the beginning of the game and see if you have a group of locations that are close to each other.
Having counters close to each other is generally a good thing as it usually means it's easier for you to build up an efficient canal/rail network. Use the cards to plan your strategy. Be careful when using cards to perform other actions, try to make sure they are 'useless' cards.
Brass is a long distance race. Do not be concerned if you are behind on victory points at the end of the Canal Period. There are many more points available in the Rail Period, and it's common for the early leader to fall behind in the second period.