Holding the pit "narrow" (pointed) side up, stick three toothpicks into the middle section at even intervals, just enough to give a firm hold. This will allow you to balance the pit on the inside of a cup, without completely inserting it into the cup.

The pit should sit in about 1 inch (2-3 cm) of water, so keep this in mind when inserting your toothpicks.

Don't insert the toothpicks to deep into the pit, this could damage it and it wouldn't grow anymore.

The shown avocado pit on the pictures hasn't the perfect shape with a pointier side.