stay behind:  We like to stay behind in the office after five o’clock for a nice chat. (To not leave a place after others have left)
stay in:  I’m staying in tonight to finishe some office work. (To not go out of one’s house)
stay on: She failed her exam, and had to stay on at school for another year. (To continue to do something, or be in a place after others have left)

stay out:  He sometimes stays out late for a drink with colleagues after work. (To stay outdoors and not come home, or come home late)

stay out of:  I was told to stay out of their arguments and mind my own business. (To not get oneself involved in something)  

stay up:  Tonight we are staying up to watch a football match on television. (To not go to bed at the usual time)

step aside:  There were calls for him to step aside when his health began to fail. (To leave one’s office or position) 

step down:  The minister who was involved in a sex scandal was forced to step down. (To resign from an important job or high position)
step forward:  A third candidate has stepped forward in the leadership contest. (To offer one’s help or services)  
step in:  The leaders had to step in to resolve long-standing disputes between the two factions of the party. (To become involved in order to help)
step out:  I need to step out for some fresh air. (To go outside for a short time)
step up:  The police are stepping up surveillance of the building used by a suspected criminal. (To increase)

stick around:  Let’s stick around until he arrives, then we will go for a meal. (To remain somewhere for some time)

stick at:  We decided to stick at it until we completed the 5,000-piece jigsaw. (To continue doing something in spite of difficulty)

stick by:  You must stick by your promise to help us to get this done. (To honour one’s promise, obligation, etc)

stick by:  The children promised to stick by their single mother through thick and thin. (To continue to support someone in spite of their having problems)

stick out:  He donned a party hat with a feather sticking out of it. (To protrude from something)  

stick out:  She stuck out her tongue as requested by the doctor. (To hold something out towards someone)
stick out:  With his towering height, he certainly sticks out in a crowd. (To be easily noticeable)

stick it out:  If we just stick it out, I am sure we will find a way out. (To tolerate something until the end)   

stick to:  Stick to the point, otherwise our meeting will never end. (To do or use the same thing and not change to something else)

stick to:  Every time you make a promise, you never stick to it. (To honour one’s words)

stick together:  They have always stuck together since their immigration here. (To be mutually loyal) 

stick up:  A stranger tried to stick him up, but he fought him off. (To rob someone)

stick up for:  Will you stick up for me? There are too many of them. (To support or defend)

stick with:  I have stuck with the same barber for the past seven years. (To continue with someone or something)  

stop by:  Will you be stopping by the supermarket on your way home? (To make a brief visit to a place)

stop by:  Jack stopped by Jill’s with a present to wish her a happy birthday. (To make a brief visit to someone)

stop in: He stopped in at a florist’s on his way to visit her. (To visit a place briefly)

stop in:  She decided to stop in to do her laundry. (To stay in)

stop off: We stopped off in one of the coastal resorts for a day before leaving the country. (To make a short visit to a place on the way to one’s destination)

stop over: They stopped over in Moscow for a night on the way to London. (To stay for a brief period before continuing one’s journey)

strike back:  The guerrillas struck back by killing two soldiers for a bomb attack the previous day. (To make an attack in return for an attack made by the opposing side)

strike down:  He struck the man down with a single blow of his iron rod. (To hit someone hard)

strike down:  He was struck down by polio at an early age. (To kill or make someone unable to act in the normal way)

strike off:  He should be struck off the roll of solicitors. (To remove from the official record, list, etc)

strike on:  We struck on the idea of being freelance journalists while chatting in a train. (To discover or think of something, especially by chance) 

strike out:  Her name was struck out as she had withdrawn from the competition. (To draw a line through something in a document to show it is not applicable)

strike out:  She left the quartet to strike out on her own. (To start to do something independently)

strike up:  He finally found the courage to strike up a conversation with her. (To begin a friendship or conversation with someone)

strike up:  An expectant crowd gathered as the band was about to strike up. (To start to play)

swarm with: On weekends the zoo is swarmed with visitors. (To be crowded with people)

swarm with: The carrion of an unknown animal was swarming with flies. (To be overrun with something)

switch off:  She seldom switches off the computer when she has finished using it. (To use a switch to turn off light, television, etc)

switch on:  Some cars have already switched on their lights before it gets dark.(To use a switch to turn on light, television, etc)

switch over:  They are going to switch over to the new teaching method. (To replace a way of doing something with another)

switch over:  Why do you keep switching over to another channel? (To change from one television station, etc to another)