There are many, many factors which contribute to smooth performance of a computer and to smooth game-playing in general. Without knowing the specifications and type of computer, it's hard to say what may or may not help you directly since what can be done with one kind, such as a desktop, cannot always be done to improve a laptop's performance due to how the two forms of the computers are made.
With this in mind, we can look at some of the general factors which will help with smooth game playing.
* A Clean Computer
A dirty computer inside will cause the machine to perform poorly due to heat build up. Computers don't like to be hot. The components work hard to push the electrons and bits of data around, and this process generates heat. Playing a game, or doing other computing-intensive applications such as graphics processing, 3d modeling, and lots of other data work, cause the components to work harder. The harder the components work, the more heat they generate. The processor (CPU), video card (GPU) and other components have safeguards built into them so that if they get too hot, they will slow down so not to burn themselves out. Sometimes, they can't cool off by doing this and will actually shut themselves down, and turn the computer off.
The way to keep the computer running cool is to put in fans and blowers into the case and on the chips. These fans spin quickly and move the air around and generally do a good job if they are clean. Once the dust builds up inside, the components really have to work harder in the heat and lose performance.
Cleaning the computer is generally an easy operation, but if you're afraid of breaking anything, have a computer "expert" do it for you. Using some canned air, which you can get at an office-supply or computer stuff store along with some coffee stirrers the computer can be blown out.
Simply stick a stirrer or even a twist-tie into the fans to prevent them from spinning and use the canned air to blow out the dust and dirt. The reason why the fans are stopped is to prevent the strong blast of air from ruining the motors and bushings, or from breaking the fan-blades. If you do this often, you might want to spring for the inexpensive bulb-nozzle blaster called a Rocket, which you can get on Amazon or from B&H Photo, for example. For less than the cost of 3 cans of air, or about $12.00 you have a green and permanent solution to blowing out the dust.
Laptops are a bit more difficult to keep clean due to their closed up nature, but putting a stick into the fans and blowing out the air with the blaster or canned air will work pretty well.
In any event, NEVER, EVER, EVER, use a vacuum! A vacuum will zap everything and kill the computer with static electricity.
Cleaning malware and running a good antivirus
These nasty bugs will run in the background and steal not only your information or worse, but will also make your computer run really poor. You can generally tell there's something wrong because you'll see lots of disk access even when you're not doing anything that requires it. Clicking on your browser takes a lot of extra time, there are pop-ups when there shouldn't be, and there's stuff in those pop-ups which you don't want to see. Sometimes they don't even produce pop-ups, but are doing stuff in the background and stealing resources for whatever nasty stuff they do. Running a good system cleaner such as CCleaner, and your antivirus program that you keep up-to-date, is one way to prevent the crud from building up.
Adding more RAM (DIMMS)
Ram DIMMs are generally an inexpensive upgrade to a computer. This, however, can be a bit complex due to the kind of memory you have inside, and the size. In some cases, what is installed can be added to, but in others what's there gets taken out and replaced with new. There are other technical things to watch out for, and in some machines there is no way of adding more RAM such as in some laptops because the RAM is soldered to the motherboard.
But anyway, why a lot of RAM if you can upgrade is helpful. RAM DIMMs are among the fastest components in your computer, and way faster than your hard disk and even your video card in some cases. This is why it is quite expensive, even by today's prices, and why some companies chintz out on the amount put in their machines when they sell them. When a computer is working, the programs put their most-often accessed data into memory (RAM) for processing. There's generally not a lot of room to hold everything, but there's room enough to operate on the current stuff and then some.
Having more RAM means the operating system doesn't need to move stuff back to disk (swap) while it's doing other things at the same time. Think of RAM as taking all your stuff out of the boxes and putting in to a room. The problem is we run out of space and need to put stuff back in (swap) stuff in and out. This swapping stuff to disk process wastes time and causes performance to drop. With more memory RAM DIMMs, you have less swapping and better performance.
If you can upgrade your machine, it's best to do so. There are limitations such as how much your motherboard supports, and whether you are running a 64-bit operating system such as Windows 7 or later.
Defrag your hard drive
(Note: This applies only to platter hard drives and not SSDs).
The hard disk, or permanent storage devices in your computer are byfar the slowest devices even today. They are lightning fast compared to those from a decade ago or longer, but are still the slowest device. The problem is disks will get slower over time due to how the files are written to the disk.
When data is written to a disk it is written sequentially and to the first open places it can find. This is fine when a disk is empty and there's plenty of open space to write the data contiguously - meaning all the bits and blocks are kept together. When a file is deleted, there's then an open space or spaces. When new data is written, the program will write parts to that new open space before it finds another space to write. If the file is the same size, everything can fit back in with no performance problem. If the data is bigger, then the parts that fit will go into that space first, then the rest will go to another part of the disk. Since the disk has heads that have to seek out the data and move back and forth, all this movement slows down the computer performance.
The solution is to defragment the disk. Using the built-in into Windows disk defragmenter, or some other program such as Diskkeeper, we can do this manually or automatically. Windows will want to do this once a week by schedule, but if you use your computer often I recommend doing this manually.
Related to the disk stuff is disk space. If the operating system can't swap stuff around easily between RAM (DIMMs) and the hard drive because there's low disk space, then it's necessary to free up space or add in another drive. The operating system may have to divvy up the data into more smaller chunks causing even worse performance. Drives are relatively inexpensive, and the solutions range from external to internal, and all this depends upon the kind of computer such as desktop versus laptop.
And finally upgrade the video card (Desktop only). If you can afford to upgrade the video, do so as this can always make a difference in the performance for the better. Before you plan on doing something like this, ask computer experts or others that know about this stuff. There are threads in the forums on hardware which will help.
Anyway sorry for the longwinded answer, but I hope this helps with the performance question. In case you are wondering here's my computer:
Intel i7-5930K @3.5GHZ
64GB RAM
GTX1080Ti video
3x Hard disks: C: 500GB SSD, D: 2TB HD, E: 2TB HD, F: 3TB HD.
