Setting the mood

Sound and music

Music is possibly the biggest tool you can use to help players be immersed. Sound has the incredible power of altering the way we feel and think, so by using ominous music in a cave or a bright jingle for a tavern you immediately set the mood for not just the game, but for each individual scene.Just think of how music is used in movies, tv shows and other media.

There are countless playlists on YouTube, websites with tabletop music and just regular movie soundtracks you can use. I personally use music a lot, I even plan out which song I'll use when and often spend hours going through lists upon lists of soundtracks to find songs I like for a campaign I'll run. I've even created my own songs, available for free on this site, which will hopefully help you set the mood for the scenes in your campaign.

Scents

Using scents is a technique not many people use, but it's one that is as powerful as using music. Scents are capable of triggering memories unlike any other sense, so using the right scents could remind players of specific real life locations, like a beach, or even of past campaigns.

Obviously scents aren't as easy to use as music or voices and I recommend using only a few during each session, but when you use them correctly they can lead to incredibly memorable moments. Consider the following example:
"You make your way into the murky town and, after spending a little while navigating through the muddy streets, make your way to the location of Madame Eluva's little shop. As you enter the scent of cheap perfume fills your nostrils before you're greeted with a hearty welcome."

Next time the party encounters Madame Eluva you pretty much only have to mention they smell something, spray the perfume and they will know exactly who it is, even if they don't remember the name of the character. Using scents like this could create some great surprise reveals, but they could also be used to simply set the scene.

As far as scents go there's plenty to use. Candles, incense, potpourri, scented oils and so on. There are even candles for sale on the internet specifically aimed at tabletop gaming, but if you prefer to make your own I've written a tutorial on this as well, which you can find here.

Sight

The one way most people help their players be immersed is through sight. Maps, mini figures, boards and other tools help not only with planning everything as a GM and with keeping track of where characters are, but it also helps with immersing everybody in the same world.
With visual representations of your world all players will imagine roughly the same world, rather than each having their own individual interpretation of your descriptions. Obviously it won't be the exact same for everybody and it depends entirely on how descriptive you normally get, but there's just something enjoyable about seeing your character on the table or about holding a map of the ruins your characters have to explore.

Light

Tied in with sight, and, in some cases, with scents, is light. Candles, mood lighting, and other forms of light can really help with immersion. A candle-lit room can do wonders, as can a fireplace. If you don't have one, or if it's just way too warm for one, there are plenty of fireplace videos on YouTube you could play on a screen. There are plenty of LED candles these days as well, which could solve both the heat, durability, and fire hazard problems you might face depending on your room.

These days color changing light bulbs are becoming more and more inexpensive too, and they can make for a fantastic way to go from scene to scene. Some work with remotes, others work through your wifi and can be controlled with your phone. Water scene? Turn to a pulsing blue. Forest scene? Turn to a glowing orange. All with just the touch of a button. Of course, don't make it too dark, you still want to be able to read character sheets, dice, and so on.

Touch

Closely related to sight is touch. Being able to hold coins, gems, maps and other props helps further immerse yourself into the world you're playing in. If members of your party are rewarded with or otherwise find a mystical amulet, ring or other piece of jewelry it's easy enough to give them a (cheap) physical version. Even a drawn picture of one could help and is usually the first thing most people use to give a physical representation of what they describe.

Taste

Gaming sessions often involve food, either in the form of a lunch, dinner and maybe even breakfast for those playing all day, or in the form of snacks. While having themed snacks is one way of creating some form of immersion you can go a step further by using food in similar ways as scents in my example from earlier.
Does your party encounter a tea ceremony? Why notl serve the players tea as well. Do they have to drink a potion of sorts and discover its effects? Create a lemonade or other beverage and offer it to the players.

Another, perhaps overlooked aspect of this is that it'll help the players with role playing their character. If they drink an unknown potion and they have a physical potion to drink they can use this experience to describe its immediate effects on their taste buds and body. If they drink tea they might feel a warm, tingly feeling in their body. If they drink lemonade it might be a tangy, maybe very sour taste.
If you're planning to use food or drinks that taste bad make sure the players know the risks. There's nothing worse than being surprised by an awful taste when you think you're getting a tasty treat. Also remember to take people's allergies into account, you don't want to be in for a nasty surprise.