Saw blades are very high-priced - the less of them you buy, the better off you will be. If you are planning on buying a radial arm saw, a miter saw, a table saw, or some combination of these saws, pick a blade size and stick with it. While there are a variety of sizes available, the most common and popular sizes are 12" and 10". If you stay with the same blade size for all of your different types of saws, you'll be able to buy one blade and use it with several saws. Over time, this will save you a lot of money.
2) Corded or cordless?
Cordless tool batteries have made considerable advances over the last several years. Tools that you would never think would have a cordless option, such as circular and miter saws, now are coming out with cordless models. If you are considering purchasing a cordless saw and you have, or may someday have, other cordless tools, consider sticking with a single manufacturer/battery system so that you can share batteries between your tools. Extra batteries are very expensive -- it is often cheaper to get a new tool than to buy additional batteries. If you purchase multiple tools from the same maker all with the same battery technology, you will have additional batteries at your disposal to complete your job, this can really increase the amount of work you can complete.
Before settling on a cordless saw, remember that even though cordless technology is very advanced today, there will be limits to the amount of work that can be done in a single day with a cordless saw. If you're a hobbyist or you don't use your saw for long periods of time, a cordless saw may be a good solution for you. But if you are a contractor the type who'll be cutting wood all day long, you may want to skip cordless technology for tools that draw large amounts of power when cutting.
Cordless saws are also more expensive to purchase and to maintain. While your cordless saw may last for 10 or 20 years; but the batteries will need to be exchanged several times during that time. In addition to the steeper initial cost of a cordless saw, you can plan on shelling out more money in the future too, perhaps repeatedly, as the batteries will need to be replaced eventually.
3) Do your reading before you buy
Saws are a big investment -- they are expensive and they see a lot of use on most job sites. Purchasing the correct saw is a big deal and even more important is to avoid purchasing a saw that you will be unhappy with. Before buying a saw, always check the internet for opinions, rankings, and reviews for the sort of saw you are thinking about purchasing. After using a saw for a week or so, you will form an opinion about it. But it's almost impossible to get a real feel about a saw just by looking at the specifications. When you read the internet for saw reviews and rankings, you will get the opinion of people who have worked with the saw and who have an informed opinion. When people have problems with their expensive new purchases, they're usually more than happy to vent and warn others. Let their bad luck save you from getting stuck with the same bad saw.
Before buying any type of large tool, read the user manual. You can find out a lot about how easy a saw is to use by looking through the manual. If it takes 20 steps that has to be repeated several times to ensure that your table and blade are square, you can be sure that this will lead to frustration in your future. If you are considering a saw where there are different cutting configurations, read the manual to find out what level of work is involved in changing the cutting configuration. If the configuration is complicated and hard to understand, it could be more hassle than it is worth and you will tend to just not use your saw this way. So even though it has some great features, if they are too much effort to use, you won't use them. So why pay for them? You can find a lot of these sorts of problems just buy reading the manual for the saw before you purchase it.