Query that uses Clustered Index Scan instead of seek - performance

Question

I have the following query that returns < 300 results. It is currently taking about 4 seconds to complete, and when I look at the execution plan, it shows that it is spending 41% of resources on a clustered index scan. My limited knowledge of database administration suggests that a clustered index seek would improve performance. How can I get the query to use a clustered index seek instead of a clustered index scan? Below is the pertinent information and the query.
Sql Server 2008 R2
Table PMDME approx 140,000 rows (this is the one that is taking up 41% of resources)
Server Hardware: 16 core 2.7gz processors, 48gb ram
DECLARE #start date, #end date
SET #start = '2013-01-01'
SET #end = CAST(GETDATE() AS DATE)
SELECT
b.total,
c.intakes,
d.ships,
a.CODE_,
RTRIM(a.NAME_) as name,
f.employee as Salesperson,
g.referral_type_id,
h.referral_type,
e.slscode,
a.city,
a.STATE_,
a.zip
FROM PACWARE.ADS.RFDME a
LEFT OUTER JOIN (
SELECT SUM(b.quantity) total, a.ref_id from event.dbo.sample a
JOIN event.dbo.sample_parts b on a.id = b.sample_id
JOIN PACWARE.ADS.PTDME c on b.part_id = c.CODE_
WHERE c.MEDICAREID = 'E0607' AND a.order_date between #start and #end
GROUP BY a.ref_id
)b on a.CODE_ = b.ref_id
LEFT OUTER JOIN (
SELECT COUNT(a.CODE_)as intakes, rfcode
FROM PACWARE.ADS.PMDME a
WHERE a.REGDATETIME BETWEEN #start and #end
GROUP BY a.RFCODE
) c on a.CODE_ = c.rfcode
LEFT OUTER JOIN (
SELECT
COUNT(a.CODE) as ships, b.rfcode
FROM
(
SELECT
A.ACCOUNT AS CODE,
MIN(CAST(A.BILLDATETIME AS DATE)) AS SHIPDATE
FROM PACWARE.ADS.ARODME A
LEFT OUTER JOIN PACWARE.ADS.PTDME B ON A.PTCODE=B.CODE_
LEFT OUTER JOIN event.dbo.newdate() D ON A.ACCOUNT=D.ACCOUNT
LEFT OUTER JOIN event.dbo.newdate_extras() D2 ON A.ACCOUNT=D2.ACCOUNT
WHERE A.BILLDATETIME>=#start
AND A.BILLDATETIME=#start AND D.NEWDATE=#start AND D2.NEWDATE'ID'
Group by
A.ACCOUNT,
B.MEDICAREID,
A.CATEGORY
) a
JOIN PACWARE.ADS.PMDME b on a.CODE = b.CODE_
GROUP BY b.RFCODE
) d on a.CODE_ = d.rfcode
LEFT OUTER JOIN event.dbo.employee_slscode e on a.SLSCODE = e.slscode
JOIN event.dbo.employee f on e.employee_id = f.id
JOIN event.dbo.referral_data g on a.CODE_ = g.CODE_
JOIN event.dbo.referral_type h on g.referral_type_id = h.id
WHERE total > 0

Answer 1

I would try creating first and index just for the colum REGDATETIME on PACWARE.ADS.PMDME table.
GO
CREATE NONCLUSTERED INDEX [IX_PMDME_REGDATETIME] ON PACWARE.ADS.PMDME
(
[REGDATETIME] ASC
)
GO
Test how it works. I would also test adding another index to the column RFCODE (same table) if the selectivity of the column is good enough.