It's a good time to check up on your W4 withholding allowances, especially if you just completed your taxes and had a very large refund or had tax due. The IRS has a helpful worksheet here: https://www.irs.gov/pub/irs-pdf/fw4.pdf
Since these allowance elections are not retroactive, please keep in mind that we are nearly 3 months into the year. Accordingly, consider modifying your initial results to factor in a "catch-up" component so that your full-year 2018 withholdings meet your expectations.
Feel free to contact me if you have any questions.