Unlike its predecessor, there is no soft reset switch or button on the windows phone. This is chiefly due to the way windows phone works. It manages RAM very effectively but that does not mean you will never experience a slow down after some days. That is when you will have to do a soft reset. There are two ways to do that.
First is the traditional way. Take the battery out and put it back in. This will reboot the phone. Second is what we recommend – press and hold the power button for few seconds until it says “Goodbye”. After it goes away, wait for 3 seconds and press the power button again (no need to hold it, just press it). This will clear the RAM and you will feel a slight bump in speed too.