Patience is key! Even skillful players lose most of the time, so expect to take a long time before you experience your first win. Just keep at it, and hone your strategy, and eventually you should be able to beat this game.
No matter your skill, luck plays a big role. And bad luck affects you more than good luck. Even if you get off to a great start, one bad deal from the lower right can turn the tables in an instant. A terrible start, on the other hand, will usually not turn around no matter what cards you get later on. Accept this.
Every game is technically winnable if you played the cards in the right way. But since you don't know what order the cards will come in, it's pretty much impossible to know which order to play the cards you're dealt.
There's really not much you can do to prepare yourself for a click on the lower right hand card pile. You either get lucky or you don't. The more cards you can stack and uncover, the greater your chances are, but there are no guarantees.
This is a game where athe ittle things make a big difference later on. That's why getting all the cards exposed and using free slots to line them up by suit are so important. When you do that stuff a lot in the beginning you find yourself with a lot more options in the midgame.
Be thorough, take your time, and make sure you aren't forgetting anything. Playing this game properly takes a lot of time. When you are cleaining up cards using free slots, especially, you might find yourself moving cards back and forth a lot to get cards of the same suit lined up as much as possible.
Kings suck. If a stack has a King on it, that means you can't touch the cards below it unless you use up a precious empty slot. Of course, if you manage to clear away a whole suit you can get rid of the King, but by the time you reach that point you're usually close to winning anyway.
Aces also suck too. Not as much as Kings, but you can't stack other cards on them which is annoying if you draw a lot of them.
I recommend you stay away from the "hint" function. If you don't already know, most versions of Spider Solitaire come with a "hint" function in which the computer will highlight two cards for you to move on top of each other. The problem is the hint function only thinks one move at a time, so it will miss a lot of the options which involve moving multiple cards. It also will not tell you to "clean up" your cards using empty slots, which is key to winning. On easy level, the hint function will get you through but on the higher difficulty levels it will steer you wrong. Don't use it.