A safe and effective method of using Ladybugs to control Aphid infectations is look around your neighbourhood for an Aphid infested plant. Look on the underside of the leaves for Ladybug eggs. The larvae stage is the most voracious, and most preferred as the larva cannot fly away! The eggs are generally a very bright almost neon yellow or orange or red. They are very tiny, approx. the size of the ball in a ballpoint pen, but they are very visible. They will be laid in very precise rows of 2-3 rows of 6-8 eggs. Sever the leaf they are on from the plant, or preferably the stem and a few other leaves.
You can either carve out the portion of the leaf the eggs are on and secure it to the plant you want the larvae to hatch on, or take a section of the plant with the eggs on and make sure you get a few Aphids on it and put it in a jar. They should hatch in a 1-3 days after which you can place them on your plant.
If you are can't find eggs, jar a few Ladybugs and a good supply of Aphid infested leaves, a few small airholes is enough as you want inside of the jar moist, but no pooling of water in the bottom. Keep them at a moderate temp, 68-72 degrees if possible and keep the jar out of direct sunlight. Check periodically for eggs, remove the leaf they are on, scrape off any Aphids, and apply to your plant with a paper clip or loose rubber band.