Off the top of your head, can you beat out a tempo of 90 beats per minute? 79? 118?
Whether or not you are a human metronome--or just think you are--it's important to note the suggested metronome markings at the top of each hymn and practice and accompany at the proper tempo. If you don't own one, it is time to purchase or borrow a metronome.
Meeting with the music leader in advance of services to run through the hymns is also very important, so that any tempo inconsistencies can be worked out before it's too late, and to make sure you both are on the same page, musically speaking.
Why is tempo such an issue?
In my opinion, one of the most dramatic examples of improper tempo is in the Easter hymn, "That Easter Morn," hymn number 198.
Here I am playing it at 82, which is the approximate tempo that I've heard it played most often.
It sounds like a funeral dirge or a hymn tune to reflect on Christ's death. Yet if you read the words, this song is celebrating His resurrection. The suggested metronome marking is 92-108, so I set the metronome at 100. Listen to the difference.
This hymn now sounds full of hope, and the music now matches the words.
It's also important to keep a consistent tempo throughout the entire hymn. I was amazed when I began practicing the organ to learn that "I Know That My Redeemer Lives," hymn number 136, is almost always played with a ritardando in the final stanza on each verse. Save the ritard for the final verse, and see how your congregation responds.
My challenge to you is to start practicing with a metronome (if you aren't), so you can see where your tempos are inconsistent, or where they are too slow or too fast, and see what difference it makes in your congregation.