I want a nice ghost follow me and help me. So I can have a friend when I'm bored or when I need motivation

There are no such things as nice ghosts.
1. majority of people do not even believe in any ghosts
2. of those that do, the majority feel they are all evil and the nice ones only pretend to be nice to get close with you

So you want a ghost like Casper?

I have to wonder, if it was as easy as asking someone how to do it, why wouldn't we all have friendly ghosts following us around? On the other hand, I could look at it like this...why should a spirit be enslaved to you to keep you occupied when you're bored?

But anyway, what Fr_Chuck said...and I'll add...don't play with things that you don't understand.

They don't always stay with you all the time its really the ghosts decisions when it wants to see you.
A guirdan angel is really all you need, ghosts only comes to ask you for help so pretty much you can't make them follow you. Some ghosts makes you follow them to the light so be careful not all ghosts are friendly by the time you reach to the light you'll be dead!