Well, there are a few tried and true methods though invoking a spirit to appear when they don't want to never really makes them happy. Mirrors are extremely powerful tools when trying to conjure spirits (hence the games kids play like Bloody Mary, etc.) If you want to invoke a spirit I suggest you settle yourself mentally before you begin because what appears to you in the mirror may startle you even if what appears isn't grotesque. However my husband has conjured spirits that gave me nightmares for 3 days. But, if you are working with what is supposed to be a white spirit it won't be bloody, gory, scary, etc. but it might be startling.
Either stand using a bathroom or vanity mirror or if you want to use a smaller mirror place it on the floor and sit down directly in front of it leaning over into the mirror. Now, some people turn off the lights and use candles... it does help set the atmosphere but it is not necessary.
Place the object with the spirit in your hands or if it is too big place it in front of the mirror. This works every time with human spirits and may take a few tries with other entities.
Once in front or over the mirror recite (this is only the invocation for white/positive energies):
Little friend in my looking glass come out to play
I ask you be a companion haunting me today
Show your face little friend, let me see you shine
I am your beholden and you, dear friend, are mine
For Dark Arts visualizations, which may be startling or frightening to some, is:
Those who dart in the shadows
Those who stroll within the sun
All that seek the liberty of choice
Who know the sides of the Universe
Reveal yourself to me
In full force of your estate, if willing
Immediately you should see something in the reflection. You can try this as many times as you want if you do not get results the first time. You are not going to damage anything by doing this.