I needed a new double bed for one of our spare rooms (that had been used for storing suitcases, etc.) and looking at what was available, decided to make my own.
I settled on standard timber sizes - 4x4, 6x4, 8x1, 4x2, 1x1, etc. and used pocket-hole joinery to tie it all together.
As far as tools, a drop saw, battery drill and hand router/trimmer, along with measuring/marking/squaring tools.
The bed rails and stretchers are 6x2 Meranti (a local timber in SE Asia where I live), the posts are 4x4s, the support rail in the centre is a 4x2, the head and footboards are finished with 8x1s.
The slat support cleats and centre support rail were rough-sawn, the rest of the timber was planed - my thinking being that no-one would see either of those and I had a bunch of 4x2s lying around.
Very little measuring was done, other than for cutting the lengths of timber - I just cut a piece of timber to act as a spacer to ensure I had the rails and stretchers at an even height and set back from the edge of the 4x4s.
All measuring was done in metric, as that's what I am used to - so the 4x4s are really 100x100 - and after planing, 90x90, but my router bits are imperial, so I decided to use inch measurements in descriptions. The plans are in metric, but if you want them in inch, just change the 'model' to inch.
The 4x4s had a 1/4" groove 7/8" deep routed in to take a matching 'tongue' routed into the boards, which were glued in place. one 8x1 board in the foot and three in the headboard gave it a nice balance and reduced the need to rip any planks. The 4x4s were cut to accommodate those plank dimensions. The tops of the head/footboards were a ripped and shaped 8x1 board.
I routed a v-groove in the sides and foot to break up the expanse of timber, sanded it all down and used a dark stain - local meranti varies so much in colour, from golden blonde to ashy dark, that staining is pretty much compulsory.
As to method:
Cut rails, cut posts, cut stretchers - test fit.
Make 'spacer'
Drill pocket-holes in rails and stretchers
Route groove in posts, route v-groove in rails and foot stretcher.
Support end of rail, use spacer to get correct height against post and seat pocket-hole screws - same at the other end and for stretchers. This almost completed construction :)
Measure and cut slat - fit support cleats and centre support rail using slat as template/guide.
Use slat as template for cutting the rest of the slats - test layout/fit slats.
Glue boards in footboard and headboard.
Cap footboard and headboard with ripped board - panel pins and glued.
Finish sand, wipe down, varnish.
All in all, it is very sturdy - Meranti is heavy stuff. I could have used much lighter gauges of timber, but apart from the 6x2s, it was what I had lying around, so the dimensions almost dictated themselves.
I did do some further 'trim', by shaping the capping planks on my table saw - a quick and effective way of 'raising' a panel.
You can find the plans here: https://www.dropbox.com/sh/k99w5pik5pezmxa/pUU2TUwlKM