My Answer: People (including me at one time) think that being able to communicate with Spirit is hard. It's actually not that hard if you are willing to sort of change what your expectations are of what the experience is going to be like. If you think the hair on the back of your neck is going to rise and crackle in the wind, if you think that you're going to be hearing ghostly sounds, cupboard doors slamming in the kitchen, lights turning on and off mysteriously, it won't happen. That eerie stuff is the Hollywood part of what communicating with Spirit is. The real part of communicating with Spirit is quiet.
However, there are a few levels of intensity to it.
Basic level One that anybody can do is to just talk to Spirit. In your head, silently in your heart, mumbling quietly, or shouting into a canyon; however you want to phrase the communication, Spirit can hear you. Also, animals who have passed are as much Spirit as your great-grandfather who has passed on. It was one of the amazing things that I learned when I "broke through" to channeling was that animals can communicate with us in our own tongue and folks who lived as a person speaking a language different from our own can talk to us just fine. It's like we have so many different languages and ways of communicating while we are human, but when we are Spirit there is just one way. Anyway, whoever you want to speak with in Spirit can hear you fine. If you want to sit quietly and get into a meditative state of mind that's fine. If you want to talk while standing in line at the grocery store or sitting in your car at a stop light, that's fine too. Now, the difficult part of this communicating with Spirit is that you can't hear them. That's the part that might take longer. Actually, the guides are saying it's only difficult if you choose it so. That's guide talk. If you can be content knowing that your dog can hear you, that your relatives who've passed on can hear you and you're okay with not being able to hear them, that's fine.
Level Two has to do with opening to Spirit, being willing not to bend Spirit to our ways, to your expectations. If Spirit is going to communicate with you in a non verbal way then the hawk who circled around your house this morning was Spirit saying, "Hey". Spirit can also communicate via tools of divination: a deck of tarot cards or a pendulum.
A really good way to communicate with Spirit is by writing. Have in mind who it is that you want to speak with and begin writing. You write your part of the conversation and then you relax and pretend and begin writing the other side of the conversation. This is where you need to lift all the rules and just allow the experience to flow. No judgments. No being frightened. You walked into this. You want to communicate with somebody on the other side. Release your expectations of what is going to happen and just let it flow. If you're in a really good space just let your hand go limp on the pencil or pen and "help" things along by roughly drawing a circle. Just doodle. Less than doodling. Just scrawl out circles and see what will happen. And be patient.
Anyway, with more control on the writing instrument you could just "trust" for a few moments that the answers you receive to your questions are going to be Spirit speaking with you. Animals can do this fine too.
Communication with Spirit can also occur during your dreamtime. Just be open to the idea that dreams are a terrific place for Folks in Spirit to come and visit. Many times my pets who have passed on come to me in my dreams. I'm not always aware of them right then, but in the morning when I awaken I remember that they had come to be with me in my dream and every time it is special. If you can possible learn how to dream lucidly and have a dream where Spirit can be with you then, that would be the primo of all wonderful dreams. But, a normal dream is much more usual and is certainly special.
Also, my understanding of the process is that Folks in Spirit are not in pain anymore. They aren't upset, or angry, or vengeful. One of the guides once said dying was like waking up from a dream. They said everybody suddenly understands everyone else. There is no hate anymore.
Mostly, what works is being playful with the process. Trying different things to see what you're comfortable doing and what appeals to you. It's like phones. They all work, but there sure are a lot of different models.