Sometimes I wish I had this problem at my table.

The best way to make sure everyone has some attention and the spotlight to shine in your sessions is to keep your adventures or sessions simple to understand. One of the things I notice a lot of novices and even some experienced GMs make the mistake of doing is making these complex epics that have more business being in a novel or TV series than an RPG. This is not to say that you can't make such games, but you have to present them in such a way that you don't lose anyone you want to be involved in it. Also, it's so damned easy to overcomplicate things. Players will come up with ideas and solutions you've never thought of, no matter how savvy and clever you are, and they, themselves, can turn a session into a treatise on quantum mechanics and Beethoven's operas (that has happened at my table - I am not kidding) and then the guys who come to roll dice have nothing to do. So try to keep them focused on the situation.
Secondly, make sure that your players make characters that fit the adventure you're going to run. I cannot stress this enough. One of the main reasons why the spotlight gets focused on some players is not others is because the others have very little to contribute based on the characters they make. If you mean for an adventure with a lot of action, gunplay, Matrix and Magic, and someone makes a character that doesn't do any of that very well, if at all, like they brought a generic Face to the party who is also a stock broker or something on the side, he's likely not going to do much for the success of the run.
Third, throw everyone a bone. Sometimes, you have to do this just so your players have something to do, and other times it's to give them some confidence in their characters. Give the razorguy a mook to cut up. Give the decker a minor system to hack. Give the mage a reason to cast his spells. Give the rigger a chance to shine in vehicle or drone combat. It doesn't have to be a big deal, just a small encounter, something simple and a little rewarding for the effort, so that the players don't feel as though they're wasting their time coming to the session. When players feel as though they're not advancing enough during your game sessions, they will begin to tune out. You don't necessarily have to make these encounters too easy. In fact, this brings me to my next point:
Fourth, be ready to kill off PCs. If players begin to believe that whatever they decide to do their characters will not be seriously hurt or killed, they will tune out. A lot of GMs, for various reasons, are shy about killing off PCs, even if the player deliberately wants to suicide the character. Without a sense of legitimate challenge, or if it at all seems that you're going to fudge the dice in their favor, or decide in their favor, or prevent them from suicide, your game will eventually collapse.
BE RUTHLESS. This doesn't mean you have to be a sadist, it means that you must not care whether or not their PCs live or die. To this end, I never roll my dice as GM; my players roll them for me in front of me, or I have Fantasy Grounds do it for me in front of God and everyone. That way, it grounds the game in it's own reality. And you must be ready to make a ruling that doesn't favor the player in the slightest if it cannot logically or even theatrically, be resolved in any other way. That means if a PC puts his gun to his own temple, and pulls the trigger with a round in the chamber, kill him off. Even if he manages to shrug off the damage. Don't use the rules to save him. Even if the player doesn't like it, at least he knows you mean business, and you are not trying to keep him alive so that he's merely an actor in your play.
Fifth, organization. Sometimes, you can't get to some players because you're too busy looking up stats or rules or whatever. You should be prepared to run the game. Even if you're doing this casually, know what to expect and be ready to quickly make rulings. Bad rulings are better than no rulings, in my experience, and the longer you take to make a ruling, the more people will tune out because they don't have your attention to do anything they want to do. Also, keep the table organized. I don't allow books other than my own at the table, and tablets and smartphones have to be off the table at all times unless I give permission to use them during play, or if there's a call coming in (I'm not going to say don't answer your own phone). I have plenty of breaks during my sessions, so they have all the time in the world needed to get personal business on their phones squared away. That brings up:
Sixth, breaks. Take breaks every hour of the session. Sitting at the table for so long makes anyone weary. Get everyone up, walk about, get something to eat, anything. Step away from the table. You'd be surprised how well this works.
Seventh, don't let Brett Schiestrom drink caffeine. This is one of my written rules, and if you ever meet this guy, keep him away from energy drinks, coffee, cola, and tea. He will go hyper and will not stop his mouth! I have seriously thought about calling an ambulance when it looked like he was having an epileptic fit, but alas! it turned out he was just being Schiestrom.