As with Becky, over the years I have tried different things.
For labeling the plants themselves, I have found that plastic labels break or are carried off by critters; even intact, the writing tends to fade. Engraved labels add up in cost, and can snap off the metal stakes and need replacement. Hand-embossed wire-on tags look potentially unbeatable (my roses each have one), but then you have to stoop close to read them. The search continues. (I am not into pencil, or those tape things that you punch the name out on.)
For notes and records, I have to confess that I got off to a very shaky start; I didn't immediately make my own plant label, and I didn't immediately record plant purchases. Because of those two things, to this day I have one daylily here which (memory tells me, and I am 99.9% sure) is probably 'Little Rainbow' - yet I cannot be 100% certain. (I know that I bought it from one garden/nursery or another on a Regional Tour. I have almost zero interest in miniature daylilies, and (with one other exception) the only reason I would have for buying one would be because there was something of special interest about it. I recall not long previously having read about polychrome daylilies, and 'Little Rainbow' in particular. I have a vaguer memory that I was excited to see 'Little Rainbow' in that garden/nursery and pounced on it. Yet, I cannot be 100% sure.)
Is she, or isn't she? ('Little Rainbow', that is.)
From such mistakes I have learned the necessity of relabeling promptly (I still have lapses on that - and pay for such lapses), and keeping purchase records.
For seedling record keeping, I used to write everything down in one of those blank journals. After I lost one journal, and another came to grief (soaked with water, writing faded), I decided I had better keep my seedling records on the computer. (Offline backups are your friends.)
(The plastic labels and the paper journals are part of the reason why some of the seedlings here are of uncertain heritage.)
I use both MS-Word and Excel to keep records on both the registered cultivars and the seedlings. MS-Word files allow for keeping extensive detailed notes such as hybridizer's hype (er, description), my personal observations, and pictures of the blooms and/or plants. I break the cultivars down alphabetically, and have several cultivar CULTDATA-i (where i = A, B, C, etc.) files which contain detailed information on each cultivar with a name starting with that letter, with one or two pictures each. (I have lots more pictures kept under a PIX directory.) If I want to review what the hybridizer said, or what garden/nursery I got the plant from (and when), or my own general notes on the plant (rusty, CMO, periods of rebloom, whatever) then I go look at that file.
Seedling observations go into different files, by the year of the observation. Eventually, if a seedling stays around long enough, it might get its own dedicated file. (I have to do a better job on that; I have the seedling pix organized well enough. Thus far, though, there are no seedlings here which I feel are introduction worthy
- though I do have some that I like enough that they have been here for several years.)
I fear that I have yet to find an acceptable way of (electronically) easily making a garden map. Right now I have MS-WORD files listing the identities of plants (daylilies or otherwise) by bed, but that is not a map. Instead, I have a pathetic text listing along the lines of "left to right (west to east): lantana,
Heuchera 'Strawberry Candy', 'Hip to Be Square', 'Polly Wolly Doodle',
Rosa 'Carefree Wonder', 'Osterized', 'Magical Indeed'...".
Excel is okay for summarizing data (nursery source, bloom size, scape height, season, etc.), but is especially good for managing plant purchase lists and recording bloom time periods. For plant purchases, the garden or nursery goes in one column, the plants on order (or received) go in another column underneath/beside that name, and things like date ordered, cost, brief plant description go in other columns. Plants on order but not yet received are in one color text; plants received but not yet potted/planted are a second color; plants finally planted out are in blue (pots) or black (ground).
(The downside of using Excel to track plant purchases is that - if you make that mistake - it relentlessly adds up the ever increasing total cost for you. Just to let you know.)
For recording the bloom period, I break the month up into 1/4 month periods; from 1-7, 8-15, 16-23, 24-end, and put a * or X in the column for that quarter-month if the daylily was in bloom. (Thus far I have only bothered recording daylily bloom times.) It makes for a very readable record, which makes it easy to compare the length and times of bloom for different cultivars or seedlings. (If more information is needed, I can put the date of FFO or LFO in the respective columns when bloom begins or ends.)
I did at one point buy one plant program - I cannot tell you now what it is/was (I never reloaded it during the last computer upgrade), but I found it cumbersome and obnoxious to use.
Slowly, the records improve...
edited to add picture of maybe-Little-Rainbow
I am also easily amused, lol. 
