行くと - "If/when go." If/when this action takes place, what follows is an uncontrollable event or state. The first part must ALWAYS be in a non-past form. Often used for something that's "naturally occurring," like a machine's function. The second part CANNOT be a command, request, suggestion, invitation or a volitional statement (unless that volitional action is an action that occurs without fail).
それは、先生に聞くと分かった。When I asked the teacher, I understood it right away. (Understanding is not volitional)
タイヤは古いと危ないですよ。If/when tires are old, they are dangerous, you know. (Danger is uncontrollable)
魚がきらいだと、日本へ行ったとき困りますか。If you hate fish, will you have trouble when you're in Japan? (Being troubled isn't controllable)
学生だと割引があります。If you're a student, there's a discount. (Being a student automatically gets you a discount)
夏になると、別荘に行きます。When it's summer, I go to my summer home. (action happens without fail)
行ったら - An state or action that takes place after the subordinate clause (~たら). Good for "If A, then B" statements. Can make a command, request, suggestion, invitation or a volitional statement. Has the broadest range of meaning and usage. CANNOT be used with counter factual statements. If the second statement is in the past tense, it cannot be an volitional action taken by the speaker.
先生に聞いたら、すぐ分った。When I asked the teacher I understood immediately. (Understanding is out of one's control)
私は大学を出たら小学校の先生になります。When I graduate university, I will become an elementary school teacher. (When the condition of graduation is fulfilled, the second action can take place)
私は忙しいですから、面白かったら読みますが、面白くないかったら、読みませんよ。Because I'm busy I'll read it if it's interesting, but I won't read it if it's not. (If it is the case that A, then B.)
きらいだら、残してください。If you hate it, please leave it. (If A is the case, <<request>>)
英語だったら分かると思います。If it's in English, I think I'll understand it. (If A, then B)
行くなら - The speaker supposes the first statement is true, and makes a statement about the present or future. Cannot be nonsensical (something that will never happen, something you cannot know for sure or something known for sure). Cannot be used if the actualization of the なら clause brings about the second clause. If the second part does not express a past or present habitual action, the speaker can express their opinion, volition, judgment, command, request or suggestion. If the second part of the sentence is in past tense, the なら part must also be in the past tense. Usually based on a previous external statement.
シカゴに行くなら、バスで行きなさい。If you go to Chicago, go by bus. (Unknown, but possible listener will go to Chicago)
杉田が来たなら僕が帰る。 If Sugita has come, I will go home. (Assuming Sugita is there, a future action will occur)
そんなに高いのなら、買えません。If it's that expensive, I can't buy it. (Assuming an item really is a certain quoted price)
山田さんが好きなら、手紙を書いたらどうですか。If you like Yamada, how about you write him a letter? (Assuming the situation, because you were told)
高橋先生なら、そのこと知っているでしょう。If it's Professer Takahashi, he probably already knows about it. (Considering Prof. Takahashi is somehow involved/knowledgeable about the situation, he is likely to know)
行けば - Gives a general conditional relationship between statements. The second statement will hold true under the conditions laid out by the ~ば statement. If the first statement is NOT an action, the following statement CAN be a command, request or suggestion. The ~ば statement CAN be past or counterfactual, but CANNOT be a single, factual past event.
これは松本先生に聞けば、分かります。If you ask Matsumoto-Sensei, you'll understand. (under the condition of asking Matsumoto-Sensei)
その町は車で行けば三十分で行ける。You can get to that town in 30 minutes if you go by car. (Car, as opposed to any other means of transportation)
安ければ買います。If it's cheap, 'll buy it. (under the condition that it is inexpensive)
時間があれば、京都へも行きたい。If there's time, I want to go to Kyoto too. (I don't know if I'll have time or not, but assuming I do)
見たければ、見なさい。If you want to see it, see it. (Under the condition that you want to see it)
できれば、これもやってください。If you can, please do this too. (Under the condition of you being able to)
その本を読めばよかった。It would have been good if I had read that book. (Had you read the book, but you didn't)
宿題をしなければならない。It won't do if you don't do your homework. (Under the condition you won't/don't do your homework)
井上さんといえば、昨日話しに行った。Speaking of Ms. Inoue, I went to talk to her yesterday. (Idiomatic use, of ~ば)
行くんだったら - combination of explanatory の and ～たら
行くのなら - Fancier/written なら statement
行くとしたら - An unsuccessful action was attempted.
行くことになったら - Under the condition that you will be made to go... (～たら statement)
行くならば- Super-fancier なら statement
