How do I determine how much federal tax I should have deducted from my pension checks to avoid a penalty at the end of the year?

Generally, a taxpayer will not have to pay an estimated tax penalty if they make payments equal to the lesser of 90 percent of the tax to be shown on their current year return or 100 percent of the tax shown on their prior year return (110 percent if their income was more than $150,000).  So, as long as you have as much tax withheld in 2019 as you owed on your 2018, you won't have a penalty on your 2019 return.