I was asked to write a bit about obtaining visualization skills. At one time, this skill alluded me, now I can think candle and 'see' candle or any other thing I so desire. As to the hows and whys, I can give no direct answer but I can list some things that came into play.
Ritual work, I have done about 1,000 Lesser Banishing Ritual of the Pentagrams (LBRPs) over the last three or four years. This simple little ritual has many simple little things to see. The sheer effort and focus of trying to see that many times is a factor.
I've done about as many Middle Pillars. These two have simple visualizations but also raise energy. The ritual slowly teaches one how to raise and manipulate astral energies. This is a factor because often what you begin seeing is this energy as it is being moved about by the LBRPs or used by various spirits.
I have done a lot of magick regarding thought-forms or, as some call them, artificial elementals. These are astral memes made of one's own energy. For me, it was easier to see my own at first. When you're doing the sort of ritualized magick I do, there are minimal distractions and you can play with environmental lighting conditions.
I also have a spirit in my employ that specializes in astral sight that gave me a boost. A boost I say because I could see before I contacted him.
The question made me realize that I had seen almost from the beginning but didn't really believe I was seeing because the images were so faded. I could always see but not with much acuity. The more confidence I have the better I see. However, believing isn't seeing. I would not advise trying to convince yourself that you are seeing what you're not.
Basically, all this boils down to is do it! Practice seeing even when you can't. Work hard, even when you don't want to. Be aware that other senses can make up for the inability to see as you begin. Pay close attention to other clues. A sports talk show radio host said today, "Unless you are doing something to make it happen, it is not a goal. It is a dream." My advice: Do Something.
P.S. I'd also suggest reading Strategic Sorcery. This is an excellent blog. You may gain some tips.