Choose a blade size
Saw blades are extremely pricey, the fewer saw blades you buy, the happier your wallet will be. If you plan on buying a miter saw, table saw, a radial arm saw, or some assemblage of these, pick a blade size and stick with it. While there are a variety of sizes available, the most popular and common blade sizes are 12" and 10". If you stick with the same blade size for all of your saws, you will be able to buy one blade and use it with several saws. In the long run, this will save you hundreds of dollars.
Corded or cordless?
Cordless tool batteries have made remarkable advances over the last several years. Tools that you would think could never be cordless, such as circular saws and miter saws, now offer cordless options. If you are thinking about purchasing a cordless saw and you have, or may have, other cordless tools, consider staying with a single battery/manufacturer system so that you can share batteries amongst all of your tools. Additional batteries are very expensive -- it is usually cheaper to get a brand new tool than to purchase replacement batteries. If you buy several tools from the same maker all with the same battery systems, you'll have extra batteries available to finish your task, this can significantly increase the work you can complete.
Before settling on a cordless saw, don't forget that even though cordless technology is very advanced today, battery life may restrict the amount of work you can complete in a single work period. If you're a hobbyist or you don't use your saw for extended periods of time, a cordless saw may be a good solution for you. But if you are a contractor the type who will be cutting wood all day long, you may want to skip cordless technology for tools that draw large amounts of power.
Cordless saws are also more expensive to purchase and maintain. 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 battery operated saw, you can expect to be spending more money in the future, perhaps repeatedly, as the batteries will need to be replaced eventually.
Do your reading before you buy
Saws are a large investment -- they are costly and they get a lot of use on most job sites. Purchasing the right saw is a big deal and even more important is to avoid buying a saw that doesn't work for you. Before buying any saw, always surf the internet for opinions, rankings, and reviews for the kind of saw you are thinking about getting. After using a saw for a week or so, you will form an opinion about the saw. But it is almost impossible to get the correct feel for a saw just by studying the specifications. When you check the web for saw reviews and rankings, you will get the opinions of people who have laid hands on the saw and who have an informed opinion. If people have problems with their expensive new purchases, they're usually more than happy to let other people know if something is not good. Let their bad luck save you from getting stuck with the same bad saw.
Before purchasing any type of large tool, read the user manual first. You can find out a lot about how easy or hard a saw is to use by looking through the manual. If it takes a whole bunch steps and an iterative process to make sure that your saw blade and table are square, you can look forward to spending more time setting up your saw than using it. If you are considering a saw where there are different cutting configurations, check the manual to find out what is involved in changing the configuration. If the process is complicated and not easy to understand, it may be more hassle than it is worth and you will be inclined to just not use your saw this way. Even though the saw has some cool features, if they are too difficult to use, you will not use them. So why pay extra for them? You can flush out a lot of these sorts of issues just buy reading the manual for the saw before you buy it.