Like any book, the Torah is easier to read when fully punctuated. Unfortunately, no common chumash or translation includes all the punctuation. In particular, you will never find a full set of quotation marks.
This is because quotes in the Torah can be very long: the longest one spans 22 chapters of Sefer Devarim. It is little use putting a begin-quote when the end-quote is so far away. But if you want to seriously study the Torah, you must figure out where each quote begins and ends. That is the only way to know who is speaking, and what the context and content of the quote is.
2. The seven speeches
Parshat Terumah begins with the verse "And God spoke to Moshe, saying:". Clearly this verse should be followed by a begin-quote, as what follows is something spoken by God. Where is the end-quote? Look all the way through parshat Terumah and Tetzaveh, and you will not find it. Only at the very beginning of Ki Tisa will you find "And God spoke to Moshe, saying:" again, indicating that we are no longer within the quote. The end-quote should apparently be placed right before this, ending a two-parsha-long speech by God.
This first verse of Ki Tisa, of course, begins another speech. But this one is much shorter. Just one paragraph later we find "And God spoke to Moshe, saying:" again, indicating the end of the second speech and the beginning of a third. The next paragraph begins with "And God spoke to Moshe, saying:", ending the third speech and beginning a fourth. And so on and so on. Check it out yourself. From the beginning of parshat Terumah to the golden calf episode in the middle of Ki Tisa, there are no physical events whatsoever. The only thing that happens is that God repeatedly gives messages to Moshe.
If you count it all up, God speaks to Moshe exactly seven times. The subjects of these seven speeches are as follows:
1) All of parshat Terumah and Tetzaveh (concerning the Mishkan) 2) The half-shekel gift 3) Hand washing basin 4) Anointing oil 5) Incense 6) Betzalel chosen to build the Mishkan 7) Shabbat
Note how there are 6 speeches regarding the Mishkan (the half-shekels collected were used for building and upkeep of the Mishkan), followed by 1 speech about Shabbat. Clearly, this is an important source for the "melacha on shabbat=tasks done in building the mishkan" idea. You build the mishkan for six days, and on the seventh day you rest.
3. The division of speeches
The whole section (all 7 speeches) consists of 20 paragraphs of instructions about the Mishkan, plus one about Shabbat. There is no obvious difference in material among the 6 speeches dealing with the Mishkan. So why divide them into 6 speeches, one immediately following the other? If the speeches were in fact said consecutively without pauses in between, couldn't they be equally well described as one speech?
Perhaps, then, there is really no distinction between the speeches. They were really one long speech, and the last 6 paragraphs were arbitrarily introduced with "And God spoke to Moshe, saying:", so that the 7-speech/7-day pattern would exist.
That is one possibility, but not the only one. There could in fact be a difference between the material in each speech. But what that difference might be is not obvious. At first glance, the long first speech seems to be about the physical aspects of the Mishkan, while the other speeches are about more peripheral matters. But why then is the hand washing basin in the 3rd speech, and why the animal offering in the middle of the 1st speech? That seems to indicate that our "first glance" is wrong.
There is, however, one common thread between the last few speeches, despite their dissimilar subjects. The half shekel, hand washing basin, anointing oil, incense, and Shabbat speech all mention "karet" or death (two comparable punishments) as a result of neglecting them.
Half shekel: "Each man shall give atonement for his soul to Hashem when they are counted, and there will not be a plague among them when they are counted." (30:12)
Basin: "When they come to the Tent of Meeting, they shall wash in water, and not die." (30:20)
Oil: "One who mixes anything like it, or one who puts any of it on a stranger [non-priest], shall be cut off from his people." (30:33)
Incense: "One who makes like it in order to smell it shall be cut off from his people." (30:38)
Shabbat: "Whoever desecrates it shall be put to death, for whoever does work on it shall be cut off from his people." (31:14)
The remaining command, the appointing of Betzalel, does not include a penalty for non-performance. Perhaps we may suggest that a person who builds ritual vessels, like Betzalel but without a Divine command, also receives the penalty of "karet". This would be similar to the oil and incense, which similarly incur "karet" if produced for improper reasons. (This command also includes open-ended permission for "wise-hearted" people to participate in the work. But perhaps that is really a repeat of the appointment of the "wise-hearted" in verse 28:3; the only relevant part here the innovative part: Betzalel's role.)
We may suggest that the above five commands, perhaps including the sixth of Betzalel, are not considered to be part of the actual "blueprint" of the Mishkan. They are necessarily precautions so that the Mishkan be built and operated correctly – so that one of the possible punishments listed will not be incurred. Since they are not part of the Mishkan, they are not listed in the Mishkan speech. And since each of them helps us avoid a different and unrelated punishment, each of them merits a separate speech of its own.
5. Priestly garments
Besides the above punishments, two punishments are mentioned in the long speech about the Mishkan itself. These concern the priest's clothing: he must wear pants (28:43), and have bells on his "me'il" (28:35), or else he receives the death penalty.
We suggested above that the warnings regarding the Mishkan were separated off into separate speeches, since they were not part of its basic "blueprint". But these two warnings are part of the much longer description of the clothing. The clothing does seem to contribute to the Mishkan "blueprint": it provides "honor and splendor" (28:2) which was an important quality of the Mishkan. Since the whole clothing section had to be included in the main Mishkan speech, the two warnings related to clothing were included along with it.
Much or all of Section 2 is based on a shiur by R' Menachem Leibtag.