In general though, we normally jump right into a mitzwah. The Noam Elimelech (very last Torah in פרשת בא) lays down a few preparations that are meant to come before the performance of a mitzwah so that once we're involved in it, we are are totally involved in it, instead of perhaps performing the mitzwah by rote, or on autopilot.
- First one should focus on the greatness of HaShem all the way up through all of the supernal realms, as far as one is able. (to the limit of one's abilities and level)
- Then, we should ready ourselves to bring berachah and kedushah down from that place, including the three major pathways of blessing: Bnei, Hayyei, u'Mezonei (children, life/health/zivug, and parnasa) [see my previous post explaining this a little in the context of the three watches of the night.]
- Finally we should be ready to perform the mitzwah completely [with all of its halachoth] with great joy. (For it is this great joy that creates a holy angel of the mitzwah)
The caveat is always: don't let this bog down your mitzwah observance. Perhaps try it once a day with a particular mitzwah until you have down a pattern for you that works and really increases your mitzwah observance.
The last Lubavitcher Rebbe said that it is important to make each Jew aware that every mitzwah that we do now is bringing the moshiah that much closer.. so definitely don't lessen your mitzwah observance because you want to really 'feel' the mitzwoth. Introduce this deeper mitzwah performance slowly and only in a productive fashion.
Also, the best way to perform a mitzwah, to my limited understanding, is still to perform the mitzwah with simple and pure emunah in HaShem. Without any fancy intentions at all. But, as I mentioned in this post about yichudim, sometimes we want to develop our relationship with HaShem and one of the ways to do so is through the method the Noam Elimelech brings down which I mentioned above.