Concentrate on Threats AND Errors. Generally speaking threats are external (our of your control), errors are internal (things under your control, errors you could make).
400m - you could discuss taxiing errors and possible runway incursion. At 400m can you land back at your departure airport should you have an engine failure? Not unless your aircraft is Cat2/3 and approved for single engine low vis etc.
Single runway OPS - that implies theres is more than 1 runway. Do you need to cross another runway to get to the active? Will there be more traffic and possible delays?
Always use a structure for your brief, that avoids it becoming lengthy and hard to follow. Weather, NOTAM, Fuel, Routing, Non-normals, Threats and errors. Or another option is the CTWOT brief: CTWOT / Chart/Terrain (msa)/Weather/Operational/Threats. Doesnt matter too much as long as your delivery is clear.
Have a look at the UK Aircrew regulations, GM1 to Appendix 5 Integrated MPL training course. Some good examples of Treats, Errors and Countermeasures in there.