I have a Kenmore refrigerator (model 53552200), and want to connect a 1/4" polyethylene line for the incoming water. I'm guessing the connection is something similar to right portion of the following image, but want to make sure before I go to hardware store:  
![](https://www.plumbingsupply.com/images/cleartubing-compressionadapter.jpg)  

(i.e. brass compression nut, brass tube insert and with a plastic "sleeve"; although 1/4" in my case). Does this sound right?

When tightening it, what is a good rule of thumb to avoid over- and under-tightening the connection?

**Update / secondary question:** I bought this [Watts Ander-Lign Compression Nut](https://web.archive.org/web/20150905075716/http://www.watts.com/pages/_products_details.asp?pid=6399) from the store, which says it is compatible with plastic tubing. Does a nut like this need a plastic sleeve? If not, would a different compression nut---that is compatible with a plastic sleeve---be preferred? NOTE: the picture above is NOT the Watts Ander-Lign compression nut I have---I just needed a picture of a plastic sleeve to aid my question

**update 2:** I haven't found a definitive answer on this yet, so any help you can provide is greatly appreciated :-)