Picking out a good computer is pretty easy, you just need to know the basics. If you pick out a good computer, it could last you as much as 2-3 times a computer that is not so good. So, what to look for?
The computer should look like it was built well.
The computer Operating System should not be filled with software or bloat-ware before you buy it.
The computer should have 8GB of RAM or more. If you buy a computer with 4GB or less you are risking that you cannot run much more than the computers Operating System.
The computer should have an i5 or i7 processor. Buying anything slower will likely mean that you will have to replace the computer sooner. The i7 processor has been stable and top of the line for many years. If it's in your budget and you plan to treat your computer well, go with an i7.
The computer should have an inexpensive internal graphics card, going without a separate graphics card from the motherboard can lead to serious degradation in computer performance (even when performing basic tasks).
The computer should have a Solid-State Drive (SSD) to run your operating system as well as to store other software. Anything other than a SSD will be slow and eventually need to be replaced. 256GB or greater is adequate.
It is a good idea to have a second internal hard drive in your computer of 500GB or more to store your files, photos, and other important documents. This can be a traditional hard drive with moving parts. We recommend storing your information on a different hard disk because this will allow you to take your files with you if you ever decide to change to a different computer. As well, it will keep you more organized and make backups of your data a breeze. Always, always, always make sure you have good backups of your Data Hard Drive (DHD) (yeah, just coined that).
The computer should have USB 3.0 slots, you can use these to attach backup hard drives to make backups of your Operating System and personal files. Running backups to a USB 3.0 drive will result in faster backups and faster access if you plan to use Flash Memory Drives.
That's it. Maybe it's a tall order but if you end up with a system like this you have done very well. We have been building computers like this for years and can usually make a great computer with multi-monitor support for $800 - $1,000. We rarely replace computers, usually simple upgrades are fine and those are only done once every 5-7 years.
Instead of replacing your computer every 2-3 years, try to get something that will last. You will probably save money in the long run and have a better experience when using your computer.