Let's start with the basics.
When you talk about a subject like this, the first question is usually something along the lines of "why make offerings?" The answer to this is easy: do you want to be considered the favorite child or the askhole who asks for a lot but never gives anything in return?
Offerings for spirits is like money for people. Its currency and a means of sustaining their essence. If you make offerings to a spirit that is currently helping you actively, you are giving them more juice with which to work. If you give offerings to the land in the spirits on it, you are sustaining the underlying balance and quite literally investing into the very cornerstones of your day to day reality.
It is genuinely that simple, and so for people who are paying attention and understand this, it becomes a no brainer. I've been doing this pretty much every day since I was a child, and I can attest that whenever I forget to make offerings, things tend to slow down. When I make them regularly and constantly connect with my spirits, things move more smoothly and I more fully enjoy life.
Working with the spirits of a place naturally gives you more pull in that location. If you connect with and honor them, they know who you are, and one of the sad facts is that we've largely gotten away from making any kind of spiritual acknowledgment here in the West. This makes offertory magic even more accessible, as if only a small few people are giving offerings on a day-to-day basis, it's kind of hard to screw it up.
More often than not, these entities just appreciate the effort. That same feel good response we have when someone considers our well-being and looks after us is the same thing they feel. That means that you don't have to worry so much about doing it right, but you do need to figure out how to do it more.
Making an offering is the process of dedicating energy to a spirit. This is done through your intent and invitation, and however you may decide to convey both feelings, as long as you do so you're doing just fine. It can be as simple as laying out a cup of coffee & telling the land "please share of my bounty. You have been wonderful to me and I wish to give back and support you spirits that have been kind to me."
Afterwards, when you feel or think that the offerings have been consumed, you can dispose of them in the disposal or trash. It's been my experience that spirits don't much care when they're done with the dish **unless the offering is to be used later OR this offering is to wrathful/troublesome spirits**. Both are outside of the scope of today's conversation.
If you decide that you DO want to go expert mode with this, you can take it a step further and share the emotion of the enjoyment of a thing with the spirits themselves.
That excitement that you feel towards a delicious meal can be shared. The experience of taste as you consume that feast can be shared. That sense of satiety and comfort and take from our stomachs being full can be shared. Each of these emotions are kind of currency, as they too are energy. If you imagine those feelings as being a kind of bounty in and of themselves, you can offer those too.
It's all about intent, focus, and ensuring that you have goodwill towards these beings, as energy goes where the mind flows. If you chant a mantra of "feed these spirits, feed these spirits, feed these spirits", your mind is locked in on feeding these spirits & you're good. The rest is all just a matter of practice.
Everything else is window dressing. You can modify this ritual of offering in 100 different ways & build upon your understanding and practice equally. Over time, you can even enter into transactional relationships with powerful spirits who will then watch over you, keep you safe, help you in social matters, get you paid....the list goes on and on. When you have the relationship to ask for these boons, great things happen, so offerings are the start to this practice.
I would strongly recommend giving it a shot, as the most you have to lose has a little bit of energy and a cup of coffee. If, for whatever reason, you don't feel comfortable doing this, I am happy to provide offerings on your behalf for a fee.