If you want the best results from your photography, your monitor needs to be calibrated.
Simply put, this means adjusting the ourput of your monitor to a known standard. What settings you choose is up to you and may depend on what you do with your images.
If you only ever put images online, where most people's monitors, tablets, phones etc are all over the place with regards brightness and colour balance it really doesn't matter too much. However, a 'standard' setting for web viewing is 6500k (colour temperature) , 120cd/m2 (the brightness or luminance) and sRGB (the colour space).
For making prints, a lower colour temperature and a lower brightness level is generally much preferred as this enables your monitor to represent how your image file will print much more accurately.
A printer neither knows nor cares what your image looks like on screen. The printer justs tries as best it can to replicate the data in the file you send it.
This means that if you have had prints made in the past and they are too dark, your monitor is too bright. Simple as that.
If your prints are say, too blue, your monitor is too yellow.
Prints too green? Your monitor is too red.
I am a big fan of making prints and have a few different calibration settings on my monitor for making prints. My basic editing calibration is 5800k (the colour temperature), 80cd/m2 (the brightness or luminance) and AdobeRGB. I also have the contrast ratio set to about 1:200 (which is about the maximum that prints can handle). There is no point editing on a monitor with a contrast ratio greater than that as the paper used for the print cannot reproduce such high contrast.
Even if your monitor is brand new and comes 'calibrated' do you know what it is set to? If not, you need to calibrate it to a known state.
If you borrow a KPS Colorimeter or our Spectrophotometer, you will be able to check. Details for our devices are available here
If you use the KPS/Croydon Camera House print system, it is definitely advised to calibrate your monitor to a setting suitable for print making as CCH DO NOT ADJUST your files. They print them as they are presented. If you use their normal commercial print service, their machine applies an 'auto-correct' to adjust your files for printing.
Wouldn't you rather be in control?