I use an instant-read thermometer like this one and find it to be very accurate.

Here is a link that might be useful: Instant Read thermometer

Consumer reports tested them and I'll post the results chart below.

If you are looking for an instant-read thermometer, Cooks Illustrated tested less expensive ones and liked these best:

I had several CDN and Taylor thermometers that all died within a year. My waterproof thermapen, while not cheap, has paid for itself over the 5 years I've had it. I'd highly recommend it.

My Taylor Thrutemp Digital timer thermometer has worked fine since 2006.

I'm not the most gentle cook so maybe that's why my Taylor thermometers never lasted?!