Losing the count is never fun, and seldom ends well. You don't just lose the count, you also lose a little credibility.
Until you're secure in keeping the count (you never will be), your partner can help you if he keeps it as well. If I'm doing the bases I try to keep it, and I'll ask my partner in pregame to "flash me the count regularly with runners on base." As the plate guy, it also helps to verbalize and/or flash the count regularly (I do it every pitch with runners on base).
You can use the official scorer as a backup in a pinch, but depending on what level you're working they might not even be keeping the count. Is a team charting pitches? The player keeping that chart is seldom quick enough to purposely give you the wrong count. Hey, there's always a video review
!
Bob had the best suggestion - depend on your partner.
JJ