quis, quid
When the indefinite pronoun "aliquis, aliquid" is preceded in the sentence by "si," "nisi," "num," or "ne," then the "ali-" drops off, leaving just the inflected endings "quis, quid." Consequently, "si quis" means "if someone," "nisi quid" means "unless something," etc. The way I remembered the rule was this little jingle:

"After si, nisi, num, and ne Then the ali- falls away."

ita, sic, tam
The adverbs which anticipate result clauses are not entirely interchangeable. "Sic" is used primarily to qualify verbs: "Id sic fecit ut..". The other two, "ita" and "tam" can qualify verbs, adjectives or other adverbs: "Via erat tam [ita] longa ut..". or "Tam [ita] male scripserunt ut..". or "Id tam [ita] fecit ut..".

tantus, -a, -um
This adjective for some reason always throws students off at first. It means basically "so great" but some flexibility is required to get this over into smooth English. Study carefully the way this adjective is used.

It's an adverb meaning "indeed, certainly," and is postpositive (it's never the first word in a sentence or clause.) This poses no problem. But the expression "ne...quidem" is sometimes difficult to spot. "Ne X quidem" means "not even X". Watch out for this. When you see "quidem," check to see whether there is a "ne" one word back. If you miss this construction, you'll mess up the sentence badly.

The "-sc-" inserted before the ending of the verb is call the "inceptive" or "inchoative" infix. It denotes the sense that the action of the verb is only in the process of being realized or in the very beginning stages. "Cognosco," therefore, means "to get to know" or "to become acquainted with," not "to know". In the perfect tense, the verb means "to have gotten to know" or "to have become acquainted with," and this amounts to our present tense "to know". Therefore, we translate "cognovi" not "I knew" but "I know" ("I got know.").

Look at the range of meanings for this verb. All the meanings are related to the idea of getting hold of something. Also, check the third principal part, "comprehendi". Some of the forms of the perfect tense will be identical to those of the present tense: "comprehendit" (he grasps), and "comprehendit" (he grasped); "comprehendimus" (we grasped), and "comprehendimus" (we grasped).

Confero, conferre, contuli, collatus
As I warned you, the verb "fero" is used in a great number of compound verbs -- prepositional prefixes added to verb roots. Here the preposition "cum" is prefixed to the root "fero", rendering the meaning "to bring together", or "to bring together for comparison". Look at the fourth principal part of this verb. It's not "conlatus" as you may expect, but the "-n-" of the prefix assimilates to the "-l-" of the verbal stem. You've got to be on the look out for this, because if you saw the form "collatus" in your reading and tried to look it up under "colfero" you wouldn't find it. You've got to get good at recognizing the stem "lat-" from "fero" and then allowing yourself some flexibility at coming up with the right prefix.

Se conferre
A verb common idiom with the "confero" is to use the reflexive pronoun to mean "to go" (lit. "to betake oneself"). So "me confero" means "I go", "te confers" means "you go", "nos conferimus" means "We go", "Vos contulistis" means "you went", etc.

Offero, offerre, obtuli, oblatus
It means "to offer", obviously, but look at the third and fourth principal parts: the prefix has been replaced by "ob-".

jubere, vetere
Commands with iubere (to order) and vetere (to forbid) take an accusative and infinitive construction.