Everyone wants a chance to shine though some people may find it embarrassing and best in small doses. A lot of gamers are introverts or at best nerds and many of us weak on social skills. So many gamers are not used to a lot of attention and can get flustered.
A game is a cooperative venture.
One way to insure screen time is niche protection - where everyone has a specific role and does it well. This works in some genres better than others, in many situations a generalist will be better and you should have some redundancy for important tasks.
Certain roles are cooperative and others tend towards solo play. This is important to consider when building your character as a solo role means your screen time is harder to share so you'll get les of it and at the expense of other players. That said sometimes those roles are essential!
Generally everyone should be capable at a cooperative task, typically combat. This kind of activity will be the bulk of most games and allow everyone to be involved.
Lets take a look at some typical roles...
- Detective: Gatherer of intel, essential in a mystery campaign. Generally solo but they can work together or have others around as backup. Involves a lot of GM exposition or the player asking questions. Can be boring to watch and if that is the case try to speed it up. This goes for GMs too, dont make players roll dice for everything - that takes time. Also try to prepare ahead of time and send the player a note with what they found. I like multiple paragraphs with each one progressively better and based on margin of success. I just need to snip what they didnt get because of a bad roll and send it along. However, a simple die roll tends to be unsatisfying so add color like your writing a scene in a book.
- Face: Social activity is key to most campaigns success, at least a little part. If one player they can take up a LOT of time conversing so this is very tricky to run. Multiple characters able to participate in the same conversation, say a party or group interrogation or maybe a talker and an observer, NPC's can really make your campaign feel alive - think about your favorite fiction. Likely you appreciated good dialogue and its the same in game. I use notes to help me track NPC's and details about them. I tend to improvise and add details as the players interact, also recycle fun NPC's with some minor changes. The campaign in-joke of the stereotyped NPC can be a lot of fun too. This subject could be a supplement all by itself but you get the idea. The key is to make such interaction fun for everyone and not take too long on one person. Also its a lot of work!
- Inventor/Enchanter: Supplies the party with gadgets and spends time in the lab or shop. A useful but often background role. Generally it is best left to a few die rolls and possible quests for materials. It doesn't have to be magical materials either, send others to deal with a shady tradesman or rummage through a scrapyard.
- Muscle: Combat is typical in most campaigns and generally a group activity. Its helpful to have different aspects of combat covered among the group so your able to handle most situations.
- Netrunner/Hacker: Usually a solo activity but depends on the setting and rules used. A simple die rol is rarely enough and things tend to be risky and contested so it usually needs to be played out. So try to make it fun to watch and not take too long. Be descriptive!
- Researcher: Pretty much same as detective but usually les interactive so its often not a good primary role. But the GM can add flair to what was discovered, the note thing from detective can be a treat for the player. Bonus points if you stick a few other plot hooks for later in the findings!
- Rigger/Driver: Usually just a go from here to there and a background thing. But sometimes there is a chase scene, if so others usually present so give them something to do or react to. These guys can realy help the group get around but often its expensive so they suffer in other areas and this should be compensated somehow - usually screen time. Some occasional die rolls with an interesting scene like avoiding an accident, airplane landing on the road, etc. It doesn't have to be long or often just fun.
- Scientist: Kind of like the detective, the scientist is there to solve a puzzle or come up with a weird science solution. Be descriptive and fun but watch your audience for boredom.
- Scout: This guy often travels ahead of the party or sneaks into the camp. The more people sneaking around the harder it is to avoid notice so this tends to be a solo thing. An advantage here is the group is looking for information likely to be immediately useful and just before combat. Sometimes it can be part of an investigation or other thing though. Keep it short and hopefully exciting. Try to avoid a lot of die rolls, they add tension so a few are good but too many and things odds of failure increase plus tension drops.