Lean starts with where business wants to go & what is the problem in getting there?
First Lean is about management systems or structure & second it is about processes stability.
Restructure or systemise the business to eliminate systemic waste, reduce systemic variation & eliminate straining the resources.
Based on the real problems, select the tools. Take one software development stream & map value stream. Identify what has been missed (like late shipment, poor quality, extra manpower) & do analysis & select tools. Use A3 Thinking.
1. An simple tool like kanban (scrum as referred by IT practitioners) is useful to identify how resources are loaded & how well they are meeting the daily customer requirements.
2. Heijunka to evenly load all the resources, like there are 2 coders, one has to code 2000 lines & other has to code only 200 that has to be evenly balanced.
3. Now if there is hurdle in loading then evenly, do (kaizen) improvement so that these two are evenly loaded. Do improvement to split total 2200 lines to 1100. This is systemic improvement.
4. On process side, frequent checks, ie check after writing few lines of codes for errors than checking after writing few hundered lines, will reduce debugg time.
Start with value stream map. identify gaps & select lean tools.
For more you can refer Lean product development & A3 Thinking by Durward Sobek