First, get someone to hold your pet! This is much easier done with two people. 
Don’t forget that this blog is not written by a vet. If you think that your pet may be ill, please take them to a vet.
Use the digital vet thermometer / stub-ended thermometer, lubricate the end with petroleum jelly or vegetable oil, and insert it about 3/4 in (2cm) into the rectum. Leave it in for about a minute. Normal temperature is about 101F/38.6C; anything over 102.5F (39C) should indicate a fever.
Measuring heart rate and pulse: To feel the heart beat place one or two fingers on the chest just behind and level with the elbow. The best place to feel the pulse is in the femoral artery in the groin. Count the number of beats over a period of one minute. Normal heartrate is 110-140 beats per minute, but can vary widely between individual pets. Under minor stress, such as traveling, going to the vet, can cause an increase. Under severe stress or illness the rate may reach as high as 300.