On Monday, we talked about decreasing in lace; today, we'll talk about increasing in a lace pattern. Remember these helpful tips:
* Find the yarnover/decrease pairs in the pattern and lightly circle them if that helps you keep track of them.
* Always work the pairs together.
* If you do not have enough stitches to work the paired decrease/yarnover combination, then work them in stockinette instead.

Lace pattern from the Apres Surf Hoodie
Again, let's use this simple lace pattern as our example:
Row 1: *K1, yo, k2, ssk, k2tog, k2, yo; rep from * to end.
Row 2: Purl.
As we did on Monday, we find that when you "pair up" the decreases
and yarnovers, you can see that this pattern has two halves to it:
K1, yo, k2, ssk —— and then —— k2tog, k2, yo.
To work the first half properly, you need five stitches; to work the
second half properly, you need four stitches. So besides noting where
the "pairs" are, you also need to note where they are in relationship
to each other. It helps to break the pattern up into sections, with one
yarnover/decrease pair per section.
Now we're ready to start
increasing. For simplicity, we're only going to talk about increasing
(using a simple M1) at the beginning of Row 1.
After a total of four increase rows, we have four extra stitches outside the first lace repeat, as follows:
First inc row: M1, *k1, yo, k2, ssk, k2tog, k2, yo; rep from * to end.
Second inc row: M1, k1, *k1, yo, k2, ssk, k2tog, k2, yo; rep from * to end.
Third inc row: M1, k2, *k1, yo, k2, ssk, k2tog, k2, yo; rep from * to end.
Fourth inc row: M1, k3, *k1, yo, k2, ssk, k2tog, k2, yo; rep from * to end.
Now we have enough to work the second half of the lace pattern AND continue the increasing, as follows:
Fifth inc row: M1, k2tog, k2, yo, *K1, yo, k2, ssk, k2tog, k2, yo; rep from * to end.
Here's how the next few increase rows would play out:
Sixth inc row: M1, k1, k2tog, k2, yo, *K1, yo, k2, ssk, k2tog, k2, yo; rep from * to end.
Seventh inc row: M1, k2, k2tog, k2, yo, *K1, yo, k2, ssk, k2tog, k2, yo; rep from * to end.
Eighth inc row: M1, k3, k2tog, k2, yo, *K1, yo, k2, ssk, k2tog, k2, yo; rep from * to end.
Ninth inc row: M1, k4, k2tog, k2, yo, *K1, yo, k2, ssk, k2tog, k2, yo; rep from * to end.
Tenth inc row: M1, k1, yo, k2, ssk, k2tog, k2, yo; *K1, yo, k2, ssk, k2tog, k2, yo; rep from * to end.
You've now added an extra repeat to the beginning of each row.

Icelandic Shawl (free)
You can use this same logic to work out increases at the end of a
row, just as you can use the logic presented on Monday to work out
decreases at the end of a row. It does get a little hairy to try and do
this on the fly, however, so I highly recommend either charting things
out, or writing out the shaping rows before you plunge into the
knitting, just to save your sanity.
The overall trick is to recognize one of two situations:
(1) When you don't have enough stitches near the edge to work both
the paired decrease/yarnover for the lace pattern AND the decrease you
need to work for the shaping. If you have enough stitches to do both,
do both. If you don't, then bye-bye lace pattern, hello plain
stockinette.
(2) When you have enough extra stockinette stitches to work a part
of the lace pattern properly. You might be able to work only half of
the pattern, but that's enough to keep the lace pattern contiguous.

Sandi Wiseheart is the editor of Knitting Daily.
What's on Sandi's needles? Working on my Summer Knits project...