"Good! Actually doing it is a good deal more complicated, but that's what books are for. Now my mandatory safety advice for all kinds of summoning: never call something up that you can't put down. By which I mean that before you start summoning anything, research it and make sure that you have a corresponding banishment of some kind — that you have all the materials for, and which you have rehearsed — ready to go. Only once you are confident that you'll be able to get rid of it should you start working to summon it. This applies even to supposedly friendly summons, such as spirits that you've developed a relationship with, because sometimes things go wrong. Spirits and elementals are people. Powerful people who can have bad days just like anyone else. Non-human people, who can't always tell when they're hurting someone. Although the friendlier spirits are usually better about that."
"Secondly, summoning a demon almost always makes things worse. If you think you have a problem where summoning a demon is the solution, spend five minutes brainstorming any conceivable alternative, and if any of them are possible do that instead of summoning a demon. In my more than 30 year career as a professional magician, I have encountered exactly one case where summoning a demon was the appropriate course of action. And even then, I checked with my friend Kent Nelson to see if he saw any way to avoid it that I had missed."
"Thirdly, when summoning something where getting what you want out of it will require an agreement or a contract, read and consider the contract very carefully. Ideally, write your own wording instead of signing something that a summoned creature gives to you. If you do agree to a deal or contract, follow your end to the letter. Ideally, have any necessary payments available to hand over the moment the deal is agreed to, so that you have no more ongoing obligations under the contract. Ideally, trade only in material goods and raw magical power — although that isn't always possible, especially with more powerful entities. Unlike the mundane legal system, many kinds of supernatural creature can compel specific performance, meaning that they can force you to do something you've agreed to, even if you didn't understand the terms or have good reasons to no longer want to comply. The ones who can't compel specific performance can often cause some other extremely bad outcome for you."
"On the other hand, try not to compel or force spirits. It is much, much safer to get their willing cooperation. Which can mean making friends, as I've recommended to you, or it can mean making a voluntary deal. There are kinds of magic that can compel magical creatures to do your bidding — it's just that if those kinds of magic ever fail, then you've got something with more capabilities than you (or else why did you summon it?) that is pissed off at you."
"Fourthly, if a summoning ritual includes an ingredient or step, don't skip it. Even if you think it's probably unnecessary. The components of summoning rituals might just be there for decoration, but then again they might not. And unless you understand the whole thing from front to back in extreme detail, you aren't qualified to say. On the same topic: many magicians obfuscate their notes or deliberately introduce mistakes in order to keep their secrets. If you find a summoning ritual in an enemy's library, or even just lying around in a dusty attic, don't attempt to perform the ritual until you have had time to analyze it and cross-check it for mistakes. I can offer you a textbook on how to do that, or check things myself."
"Fifthly, mise en place. Read a ritual thoroughly from beginning to end, and arrange all of the necessary components ahead of time, so that they are within easy reach. Otherwise you can end up in a situation where the next step is to place a candle on an intersection to stabilize it, but you can't reach the candle because if you pick up your chalk the floor is going to explode. These are my second eyebrows, and I pray every day not to need a third set."
"Finally, never reach inside a summoning circle or otherwise put any part of yourself inside it. If you have reached an agreement with a spirit or elemental, you can scuff out the circle with your foot in order to make it safe. The reason is that summoning circles are designed to keep things contained, and keep them from interfering with the summoning. So if you end up inside the circle, even just a little, you might find yourself stuck inside with whatever you've summoned and unable to shut it off. At that point, the only ways to get out are for outside assistance to come rescue you, or for the summoner to die and shut the whole thing down."