Is there a proper sequential order that is recommended for Bodhicitta to be developed? I am not yet familiar with the different techniques such as lojong and tonglen etc., I have just been working on developing loving-kindness towards others as an initial start.
I also had another question and I am wondering what the two obscurations are and what the (two presumably) methods there are for removing the obscurations?
In reality practices such as Lojong and the tonglen which it incoporates are extremely difficult, and are not really possible to practice without proper foundation of at the very least Bodhicitta generated with effort. So yours is an excellent question!
From what I have understood:
As the Three Principles of the Path indicate, first and foremost is a sense of renunciation towards samsara. This doesn't mean deprivation, whipping yourself, putting yourself in a hair shirt - it just means that you see through the samsaric delusion and realize that the process samsara will always be disappointing and full of pain. So you turn away from it (which is the meaning here of renunciation). You continue to work, eat etc but you don't invest in the meaningless desires etc.
Once you understand the suffering that is samsara and evince a wish to be free from the whole process of ignorance-elaboration-disturbing delusions (kleshas)-karma-suffering cycle, then and only then can you really understand the suffering of others. And that is the basis of the whole beginning of generation of what we are calling here 'conventional' bodhicitta.
It is usually presented in a way that ultimate bodhicitta then comes after this. In reality however most masters tend to agree that both forms of bodhicitta complement each other even as they are developing, and for various reasons probably too technical to go into here they ideally develop hand in hand. One without the other will not lead to Buddhahood.
As to your other question, there are obscurations which are the active disturbing mental factors (klesha) and there are others which are the residue of having had those kleshas active, kind of like a memory effect. These are much subtler and though don;t necessarily hold you in samsara they do hinder omniscience.