Position of adverbs

Here are the main rules and exceptions on the position of adverbs in sentences:

First rule: if there is only one verb in the sentence, the adverb comes before the verb as in the following example: He usually comes to work on time.
Exception to the first rule: if the only verb in the sentence is 'to be', the adverb comes after the verb as in the following example:  He is usually on time.

Second rule: If there is more than one verb in the sentence, the adverb comes after the first verb as in the following example: He has already arrived at work.
First exception to the second rule: if the first verb in the sentence is an auxiliary verb with 'to', i.e., have to, need to, ought to and used to, the adverb comes before the first verb as in the following example: He usually has to start working by 9:30 AM.
Second exception to the second rule: if the first verb in the sentence is a contracted negation, the adverbs 'probably', 'possibly' and 'certainly' come before the first verb as in the following example: He probably won't come to work on time.

These being the main rules and exceptions, there is more to this topic.  You can find more information on this webpage, which also provides you with some exercises. 

Here is another document with exercises on the same topic.  You can find the key for the exercises here.

Prepositions

Basic prepositions:
Here you can find some exercises on basic prepositions.  The key to the exercises is hereby made available. (Source: English Grammar in Use: Intermediate by Raymond Murphy)

Noun, adjective and verb + preposition:
Here you can find some exercises on nouns, adjectives and verbs which are used with certain prepositions.  The key for the exercises are also hereby made available. (Source: English Grammar in Use: Intermediate by Raymond Murphy) Here is a list of words with prepositions.

Phrasal verbs:
Here you can find some exercises on phrasal verbs.  The key to the exercises is hereby made available. (Source: English Grammar in Use: Intermediate by Raymond Murphy)

You can hereby find a link for more online exercises on the topics above.

Conditionals

Here you can find some information and exercises on conditionals.
Here you can find information and exercises on the same topic along with the key for the exercises. (Source: English Grammar in Use. Intermediate by Raymond Murphy)
Here you can find more mixed exercises on conditionals as well as other linking words that can be used in conditionals. There are also some exercises on expressing wishes.

More tips on PowerPoint presentations

Here you can find list of do's and dont's for PowerPoint presentations.

The dont's for PowerPoint

Here you can find Don McMillan's standup on the dont's of a PowerPoint presentation.

The 10/20/30 Rule of PowerPoint

Here you can find Guy Kawasaki's recommendations on the length (10 slides), duration (20 minutes) and font size (30 points) in a PowerPoint presentation.

Here you can find a stream of his pitch. ('Bozo' means 'fool'.)

Lists of three and the rule of three: two speeches

Here you can find the first part of Steve Jobs's iPhone product launch speech.
Here you can find Barack Obama's inauguration speech.
In both of them, please pay attention to the usage of the lists of three and the rule of 3s.
Here is a stream where the rule of 3s is explained among other useful tips on making presentations.