There are a lot of different types of mortgages around as well as many different lenders. It can be quite confusing knowing exactly what to look for.
The main thing to consider is the cost. A mortgage is a very long term loan and it is therefore extremely expensive. You need to consider how you will be able to keep it cheap and this will be determined by the fees and interest rates. Often a mortgage will have a set-up fee and it may also have an administration fee when you pay it off. There will also be interest charged and the amount of this is determined by the rate, which may change over time or may be fixed for a certain period.
It should be possible to work out how much the mortgage will cost for the term that you want to borrow assuming the rates do not change. The rates will change, but so will all of the lenders rates and so you are better off comparing them at the current rates. You may be able to move your mortgage to a different company anyway, if you feel that they have a better rate.
You may also want to choose a mortgage company that you trust. There are a lot of lenders out there and some are more well-known than others. You may be interested in finding one that has a good reputation or you may not worry as long as they are cheap. However, you may decide that you would like a company with a good reputation or at least one that you have heard of.
You also need to consider the repayment amounts and term. Think about the fact that you will need to be paying that much money each month for all of that time and decide whether it is something that you can afford. If it is not, then you may need to consider not having the mortgage at all. It is a big commitment and you will have that debt hanging over your head for decades and it will cost a lot of money. You will have a house at the end of it, but you will have to decide if you think that it is worth it.
So consider whether a mortgage is the right thing for you and then look at the cost to see which rate is the best. Also consider whether you would prefer certain lenders over others.