When working in lace you must always take care to match any increase (yo) with a decrease so that your stitch count remains constant (unless you are told otherwise in the pattern). If you are working a lace panel with stitches increases being worked at each side you should make sure to mark the start and end of the lace panel. When enough stitches have been increased at either side you can then include these stitches in the lace repeat and move the lace start and end markers outside this new repeat.
In our example the increased stitches are shown with a light grey background (dark grey is a 'no stitch' space). When enough stitches have been increases at each side to work another pattern repeat this new repeat is shown with a pink background. If you do not have enough stitches to complete a lace repeat just work the extra stitch(es) in knit or purl to match the pattern. In our example they are worked as knit stitches.
Above is shown a simple lace pattern.
The lace pattern repeat is shown in the red box (2 stitch, 4 row repeat). Dark grey is a 'no stitch' place holder. Light grey is an increase stitch, I'll use M1 as our increase for this example. Our new full lace pattern repeat is shown in pink.
Row 1 (RS): M1, place marker for start of lace repeat, (yo, k2tog) twice, place marker for end of lace repeat, M1.
Row 2 (WS): P6.
Row 3 (RS): M1, k1, remove marker, (ssk, yo) twice, remove marker, k1, M1.
Row 4 (WS): P8. We have now got enough stitches on each side for a full repeat of the lace (2 stitches) so we will move the markers out.
Row 5 (RS): Place marker for new start of lace repeat, (yo, k2tog) 4 times, place marker for new end of lace repeat.
Why not give this technique a try in the following patterns: