I can only share what has worked for me, and it is not always 100 per cent effective. I like to use tarot, so I begin by choosing a court card whose personality reminds me of the person I am trying to contact. I choose a second card based on the message I would like to receive. I draw both of these cards in the morning, meditate upon them, then carry them with me throughout the day . At various times throughout the day, I look at the cards or simply think of the cards/person/message I want to receive.....and I do mean SEVERAL times throughout the day...... while I'm at work, during my lunch break, while I'm watching TV, etc. This helps to imprint what I want to receive in my dreams in both my conscious and subconscious mind.
In the evening, I will do an additional, "special" meditation with candles, incense, and crystals to further imprint the importance of what I seek in my subconscious. Lastly, before I go to sleep, I leave the tarot cards near my bedside and say a prayer, requesting that I make contact with whomever I am hoping to meet in my dreams.
I know this sounds obsessive and indeed, it is, but I have found the most success with this type of persistent, focused thought. Good luck!