Credit to Brewlab, here's what they recommend.
Yeast cultures supplied by Brewlab are held on agar slopes to preserve their viability and consistency. They are stable for up to 6 months if kept in a refrigerator below 4C. They will be harmed by freezing and will deteriorate within one month if kept at room temperature.
To grow the yeast from the slope prepare a nutrient solution of malt broth by dissolving three table spoons of malt extract in 300 cm³ of boiled water in a clean sterilised flask or bottle of at least 500 cm³ size.
When cool (below 35 C) pour some of the solution onto the yeast culture and shake to suspend the yeast cells. Alternatively a flamed wire loop may be used to loosen the cells. DO NOT ATTEMPT TO DISSOLVE THE SLOPE. THE CELLS ONLY GROW ON THE SURFACE OF THE AGAR AND SHOULD BE DISLODGED BY SHAKING.
Transfer the yeast suspension into the rest of the nutrient solution and allow to grow for 24 to 48 hours in a warm environment (20-30 C) as a starter culture in your brew. Cover the bottle opening with aluminium foil or plug with cotton wool. DO NOT INCUBATE A STARTER CULTURE IN A TIGHTLY SEALED BOTTLE AS PRESSURE MAY CAUSE IT TO EXPLODE.
Ensure that the yeast is working well before pitching. It should show a frothy surface as gas is released and have a good sediment of yeast cells at the bottom. Ensure that all of these are pitched into your wort to achieve maximum speed of fermentation.
Take care when handling the culture and starter bottles to avoid contamination particularly from fingers.
Maintaining an active yeast is essential in obtaining a good fermentation and requires a good temperature control and some degree of rousing when yeast is pitched. Temperature during fermentation should be between 15 and 23C and not vary excessively. Too low temperature and the yeast will produce undesirable flavours. Insulate fermentation vessels where possible and plot temperatures to check progress.
Rousing of pitching yeast ensures that sufficient oxygen is present for the yeast to grow. This is particularly important for high gravity worts. Rousing after pitching should not be conducted as stale and undesirable flavours may develop.