We have been trying out ways to collect Birch (Betula alba) sap. We used a carved oak peg in birch-tapping kits available for £10 including postage from Touch-Wood.
You can see the whole process in a YouTube clip link from the Touch-Wood website. As the sap is rising in the Birch tree, a hole is drilled slanting upwards with a 16 mm bit, then the oak peg with a hole is knocked in and allows the sap to drip into a bottle. A hole is drilled in the bottle enabling it to rest on the peg (or it could be tied onto the tree). There are lots of uses for the sap from boiling down to syrup (which takes a while) to making wine.
Our efforts to collect Birch sap have been a bit undermined this year because we have not been able to travel back and forth to Holt Wood as often as we would like – the sap collects quickly and can attract flies if not harvested promptly. We have discovered that wine or sherry bottle corks can be readily reused as stoppers once the bottle and peg are removed.

For an alternative way to collect Birch sap see the example on the Natural Bushcraft website. And for some really super products from Birch trees see the website of Priestlands Birch in Somerset where you can obtainP1020255 a birch sap tonic or birch tar soap.
There are other ways to use Birch. If you can collect enough Birch bark in a tin it is possible to distil birch tar oil in a fire, collecting it through a small hole into another tin, it is dark and antiseptic. Our focus at the moment is on collecting Birch buds so that they can be infused in oil for making lip balm and ointment. Trying this out in recent years, we have found that the oils last a good length of time, probably testament to the strongly antiseptic and antifungal properties of the Birch in terms of its essential oil.