A bit of back ground first. Both English and tp have a basic Subject-Verb-Object format, a noun-phrase (noun plus maybe some adjectives) describing who does or is what the sentence is about, followed by a verb phrase (verb plus maybe some adverb or a copula --”be” plus a noun or adjective) telling what the subject is or does and then maybe another noun phrase telling what the subject did that to. In English, it is usually pretty easy to tell nouns from verbs from adverbs from adjectives. They are usually different words and they behave differently. Thus, it is pretty easy to tell when the subject (a noun phrase) ends and a verb phrase, the verb, begins, and, similarly, when another noun phrase, the object, starts up. In “The tall man shot the fat duck”, “shot” is pretty clearly a verb, so the noun phrase before it constitute the subject and the noun phrase after it the object.
The situation is quite different in tp: either it has no nouns, verbs, etc. or almost every word is in several of these categories or there ae many words in different categories that look exactly the same. However you describe the situation, if you just have a string of words that might be nouns or adjectives or verbs or adverbs, it is not clear where the sections are. Consider this:'jan suli utala waso suli'. It turns out that one can divided this into Subject-Verb-Object (or even without the object) almost anywhere and get a grammatical – if sometimes decidedly odd – sentence. “A man aggressively enlarged a large bird” (j/su/ws) “A large man aerially attacked a fatty” (js/uw/s) “And aggressive large man is a fat bird (jsu/ws) and so on, including, of course “A big man attacked a large bird” (js/u/ws). To be sure, context will often eliminate many of these from consideration, but not in all cases and, in some cases, we may want to say one of the less likely things – it would be news, after all, if a big, bellicose man made a large object fly (jsu/w/s). So, to be on the safe side, we need ways to say explicitly in tp what is done covertly in English by the shifting between nouns and verbs.
'li' goes at the break between the Subject noun phrase and the Verb verb phrase, where in English there is the shift from noun to verb.
'e' goes in the break between the Verb verb phrase and the Object noun phrase, where in English there is the shift from verb to noun.
So, when you have finished saying who is doing the doing but before you say what is done, drop in 'li'. And when you are done with the doing and before you get to whom it is done to, drop in 'e'.
The sentnces above look like this then:
jan li suli utala e waso suli
jan suli li utala waso e suli
jan suli utala li waso suli
jan suli li utala e waso suli
jan suli utala li waso e suli
There will be some complication – but very minor ones – when we get to compound sentences, but that is later.
There are, however, three complications which arise immediately and need to be dealt with now.
1. When the whole of the subject is 'mi' or 'sina', 'li' is NOT inserted before the verb. Note that this does no affect subjects of more than one word that involve 'mi' or 'sina', like 'mi mute' or 'sina ali', or 'tomo mi', all of which require 'li'. This exclusion also does not extend to other pronouns, 'ona' and 'ni' both of which always require 'li'.
2. the verb place in a sentence is sometimes occupied by a preposition (a small class of words which are set aside just for the following reason). Prepositions take objects, but they are not the Direct Objects of the Subject-Verb-Object pattern. In particular, they attach to the preposition directly with out an intervening 'e'. So, “I am going home” is 'mi tawa tomo', NOT 'mi tawa e tomo'. To make matters slightly worse, 'mi tawa e tomo' is a good sentence but with a different meaning, “I move my house”, where the preposition behaves like an ordinary verb (as most non-verbs can). So, in applying the 'e' rule, you need to be aware when you are using a preposition and when you are using it AS a preposition.
3. Strictly speaking, the pattern of tp sentences is more completely given as Subject-Verb-Object-Prepositional Phrase. There is no marker like 'li' and 'e' to indicate the beginning of a propositional phrase at the end of a sentence, but the same sort of problems can arise here as those met by 'li' and 'e':
'ona li pana e tomo tawa mi' may mean either “He gave me a house” or “He gave my car”, depending on how 'tawa mi' fits in. I get a car if it is 'ona li pana e tomo/tawa mi' with 'tawa mi' a prepositional phrase. I lose a car, if it is just part of the modifier string to 'tomo'. As a kindness, some people have taken to putting a comma before final prepositional strings. These are always optional but often appreciated by readers (and the corresponding voice changes by listeners).