An action can take place habitually or it can occur just temporarily. When you say you do something habitually you mean that you did it in the past, you do it now and that you expect to do it in the future as well. Consider for example, ” Mrs. Taylor’s husband goes fishing in July”. What is meant is that in the past in July, her husband went fishing, that he is going fishing now (if it is July now) and that it is expected that he will continue to go fishing in July in years to come as well. Grammatically speaking, we use the simple present to express actions that are habitual.
Not all things that we do are habitual. We can also talk about the things we are doing only temporarily at the present time. The sentence “Miss Carpenter’s husband is visiting France this summer,” does not mean that he visited France in the past or that he will visit there in the future. Therefore, he is only there temporarily (just for this summer). We express such actions using the present progressive tense. In the example it is clear that he is not finished doing the action as well as the fact that he is doing the action now at this specific time.
If let us suppose Jane says, “Ms. Hill is reading a good book by Flaubert this year,” Jane does not necessarily mean that Ms. Hill is reading the book at that very moment while Jane is speaking. But she does mean that Ms. Hill is in the process of reading it or that she is not yet finished reading the book. It is also clear that Ms. Hill isreading it this particular year. These 2 conditions would call for the use of the present progressive.
The present simple is the tense to use to express actions that occur one after the other as when (a) a sports broadcaster reports the play by play action (b) a cook demonstrates how to follow a recipe (c) a sales representative demonstrates how to follow instructions for assemblying the parts of the product together or how to operate it (d) or even when someone gives directions to a passerby about how to arrive at a particular destination.
The following are illustrations of the above respectively: (a) Pete passes to Rogers, Rogers to Bobby, Richard intercepts, Richard to Ken, Ken shoots and he scores! (b) First, I put a teaspoonful of oil in a frying pan and turn on the stove, I set the dial to medium, then while the oil is heating up I dice an onion into……….. (c) You connect part “A” into part “B”. Or, you press “c” to turn it on……… (d) You walk to the traffic lights and then you turn left and go straight for three blocks………..
REFERENCE: How English Works; A Grammar Practice Book; by Michael Swan & Catherine Walter; Oxford University Press; 1997.